added 4:30 p.m.

The successful operation by U.S. special forces Sunday killing Osama bin Laden is "a strategic blow to al-Qaida," counter terror advisor John Brennan told reporters Monday afternoon. It creates a "better opportunity to destroy it" by creating internal divisions.

But the death of the world's most wanted terrorist does not end the terrorist threat against the United States and other western nations. As we reported earlier, the Department of Homeland Security is advising government agencies to be on high alert for possible reprisal attacks.

CIA Director Leon Panetta said "terrorists almost certainly will attempt to avenge him, and we must—and will—remain vigilant and resolute," ABC News reports. "But we have struck a heavy blow against the enemy."

That threat could come from "lone wolf" terrorists as much as from al-Qaida followers. In recent years, bin Laden has been viewed more as an iconic figure for al-Qaida rather than the controlling hand he enjoyed before the 9/11 attacks. The group has split into smaller, autonomous cells and networks, and its ubiquitous Internet presence reaches an untold number of potential new recruits.

In February, U.S. intelligence officials identified Yemen-based American-born cleric Anwar al-Awlaki as a bigger threat than bin Laden. Fort Hood shooter Nidal Hasan and attempted Times Square bomber Faisal Shahzad are among those Awlaki communicated with or inspired. During his sentencing, Shahzad defiantly told the court he tried to wage war against America because he believed the country was at war with Islam.

Meanwhile, a series of plots by homegrown radical Islamists were prevented only because of pro-active sting operations initiated by the FBI.

"Decapitating the movement will not undermine it; the al-Qaeda affiliates and the singletons will still pose threats," former interim CIA Director John McLaughlin told the Washington Post. "But much of the inspirational power of the al-Qaeda center will diminish."

For more on al-Qaida's future after bin Laden, and what his death means in the fight against terror, click here.

Bin Laden's Refuge Sparks New Questions About Pakistan

added 3:22 p.m.

The killing of al-Qaida leader Osama bin Laden by U.S. forces in the military city of Abottabad, 35 miles north Pakistan's capital, marks a new low in U.S.-Pakistani relations. The FBI's Most Wanted Terrorist was hunted down by American Navy Seals - not in a remote cave in Pakistan's rugged tribal areas along the border with Afghanistan - but in a suburban city just an hour's drive from Islamabad that is home to the a Pakistani military base and the prestigious Kakul military academy.

"We shared our intelligence on this bin Laden compound with no other country, including Pakistan," a senior administration official said in a briefing early Monday morning.

Although the civilian government led by Pakistani Prime Minister Yusuf Gilani hailed the bin Laden killing as a "great victory," the Pakistani military has remained predictably silent. Reports have also emerged alleging the million dollar compound where bin Laden was killed to be a safe house for Pakistan's spy agency, the ISI.

For months, top U.S. officials have accused Pakistan's military establishment, including its spy agency, the ISI, of harboring terrorist leaders in Pakistan.

Secretary of State Hillary Clinton, for instance, has alleged that some government officials have been implicit in sheltering bin Laden and Taliban leader Mullah Omar.

"I am not saying they are the highest level…but I believe somewhere in this government are people who know where Osama bin Laden and al-Qaida and where Mullah Omar and the leadership of the Taliban are," Clinton said a year ago.

During a recent trip to Pakistan, Admiral Mike Mullen, the chairman of the Joint Chiefs of Staff, accused the Pakistani military of sheltering the Haqqani network.

"It's fairly well known that the ISI has a longstanding relationship with the Haqqani network," Mullen told the Pakistani newspaper Dawn. "Haqqani is supporting, funding, training fighters that are killing Americans and killing coalition partners….So that's at the core—it's the only thing—but that's at the core that I think is the most difficult part of the relationship."

The Haqqani network is a faction of the Taliban operating out of the lawless belt between Pakistan and Afghanistan has been at the forefront of the insurgency against U.S.-led NATO forces in Afghanistan.

In addition, several recent reports tied the ISI to jihadi groups in Pakistan, including the Lashkar-e-Tayyiba (LeT). Documents made public in July last year by WikiLeaks.org reveal the intelligence agency's links to terrorist groups fighting U.S.-led coalition forces in Afghanistan. More recent disclosures show the U.S. placed the ISI on a list of terrorist organizations due to the Haqqani network links.

A report released early last year by the London School of Economics details connections between the ISI and Afghan insurgents and how the ISI is working to undermine U.S. and NATO forces in Afghanistan. A United Nations report corroborates ISI's support for jihadist groups in the region.

Recent revelations by American Lashkar operative David Headley have also linked the ISI to the 2008 Mumbai terror attacks. Headley, who conducted reconnaissance on high-profile targets for the attacks on behalf of Lashkar, reportedly told a team of Indian investigators that the terrorist group worked hand-in-glove with rogue elements tied to Pakistan's intelligence agency.

Since 9/11 most of the senior leaders of al-Qaida captured in Pakistan have been found hiding in leading Pakistani cities: Khalid Sheikh Mohammed in Rawalpindi, Ramsi bin Al-shib in Karachi, and Abu Zubaida in Faisalabad.

For more on the ISI's involvement in terrorism, check out Sebastian Rotella's excellent reporting here.

How They Did It

added 12:51 p.m.

The National Journal's Marc Ambinder provides excellent background into the raid that killed Osama bin Laden, the preparation for it and the Joint Special Operations Command that carried out. Read it here.

Extremists React to bin Laden Death

added 11:42 a.m.

In the hours after the official announcement of Osama bin Laden's death, jihadi forums and extremist websites have been flooded with a mix of responses. Although some jihadists have welcomed the martyrdom of one of their greatest leaders, others have condemned America or appear to be in damage control mode.

As noted earlier, Hamas Prime Minister Ismail Haniyeh denounced the "assassination of the Al Qeda [sic] spiritual leader Sheikh Osama Bin Laden," using honorific terms for a story on the group's English-language website, qassam.ps.

The Muslim Brotherhood issued contradictory statements, with a somewhat conciliatory note in English and a condemnation of the strike in Arabic.

"With Bin Laden's death, one of the reasons for which violence has been practised in the world has been removed," Essam al-Erian, a member of the Muslim Brotherhood's governing body, told Reuters. "It is time for Obama to pull out of Afghanistan and Iraq and end the occupation of U.S. and Western forces around the world that have for so long harmed Muslim countries," he said.

Al-Erian's statement to Reuters matched other language found in an article on the group's English-language site, stating that the MB wanted to "clarify that Al Qaeda did not reflect the teachings of Islam adding that in fact Islam denounces violence and terrorism that is promoted by Al-Qaeda."

In Arabic, an official statement by the group used the honorary term of Sheikh with Osama bin Laden, and called him the Arabic term for a martyr, Shaheed. The statement also aggressively attacked the assassination and blamed the West for a media campaign against Islam.

"Today, the U.S. president has announced that a special task force of U.S. Marines has succeeded in the assassination of Sheikh Osama bin Laden, one women, and his children, as well as a number of his companions. [With this], We find ourselves in a new situation. The Muslim Brotherhood announces it is against the use of violence in general, and against the method of assassinations, and they are with fair trial of any accused of any crime whatsoever," the MB said in its Arabic-language statement.

"The Muslim Brotherhood calls for the world (in general) and the Western world, as peoples and governments (in particular) to stop linking Islam with terrorism, and correct this erroneous image in a deliberate way, which has already been promoted for a number of years. And the Muslim Brotherhood confirms the legitimate resistance against foreign occupation for any country, as a legitimate right guaranteed by divine laws and international pacts. It is shuffling papers [using semantics to distinguish] between the legitimate resistance and violence against innocent, as is the intention of the Zionist enemy in particular."

"And as long as the occupation remains, so too will the legitimate resistance. It is on the United States, NATO, and the European Union to quickly end the occupation of Afghanistan and Iraq, and to recognize the legitimate rights of the Palestinian people."

Shiite organizations, normally opposed to al-Qaida and other Sunni extremists, also took a subdued tone. Hizballah, which has found itself occasionally in conflict with Sunni extremists in Lebanon, did not come out in support of the attack. Rather, the organization questioned photos released by a Pakistani organization in an English article, and just reported the responses of states around the world in an Arabic article.

Somali al-Qaida affiliate al-Shabaab seemed more shocked in its reaction.

"As a cover-up to its catalogue of failures, the enemy always tries to distract the attention of not only the supporters of the Jihad and the Mujahedeen, but also its friends to a whole different direction, by coming out with a new barfaced [sic] lie that happens to be proved wrong in no time at all," said a moderator on alqimmah.net. That is a Somali website which convicted terrorist Zachary Chesser linked to al-Shabaab. "However, it seems that the enemy is still failing to realise that the Jihad for the cause of the almighty Allah does not depend on the life of a leader, despite the facts on the ground that also shows the same. It is not our goal to get that through to them.

"So, we would like to inform our brothers not to go into discussion about the current rumours till an official statement from the Mujahedeen themselves."

Shumukh al-Islam, said to be the forum most closely linked to al-Qaida, posted no official response on the main page of their site. According to the Middle East Media Research Institute (MEMRI), site administrators "erased two messages posted by members who discussed the issue, and issued a statement warning members not to talk about the matter and not to believe any media reports, but to rely only on official statements from the mujahideen: 'Have faith in Allah, be patient and do not report the rumors that are being spread! We have clarified this matter many times. By God, none of you is to write about this matter until we receive confirmed reports from those concerned.'"

However, individual bloggers in a variety of jihadi forums reacted strongly to the news.

"May Allah give you a place next to our beloved Prophet (saws), ameen amen," said one commentator on popular jihadi website Ansar al-Mujahideen English Forum [AMEF].

"The lion Osama has died… I ask Allah to grant him the upper Paradise, the company of the Prophet Muhammad and his honored companions the Mujahideen," another forum participant commented in the forum of Shabkat al-Jihad al-Alaami, the Network of World Jihad. "But let the disbelievers know that the Muslim Mujahideen pledge, Allah willing, that the hour will come. … Really, really, really America and its European allies from the West and the East will not enjoy security after today. And you will see that very, very soon… quoting the brother Abu Qaqaa Agha."

Hamas Condemns bin Laden Killing

added 10:24 a.m.

Palestinians are hoping that a United Nations vote in September paves the way to statehood for them under the newly unified Fatah-Hamas leadership.

But the two groups split Monday on reactions to the U.S. assault in Pakistan that killed Osama bin Laden. Palestinian Authority spokesman Ghassan Khatib called bin Laden's death "good for the cause of peace worldwide" and criticized "the violent methods -- that were created and encouraged by bin Laden and others in the world."

Hamas leader Ismail Haniyeh, on the other hand, had blame only for America. "We condemn the assassination and the killing of an Arab holy warrior," Haniyeh told reporters. "We regard this as a continuation of the American policy based on oppression and the shedding of Muslim and Arab blood."

"We ask God to offer him mercy with the true believers and the martyrs," Haniyeh added.

The statement evokes memories of gleeful reactions among many Palestinians who celebrated the 9/11 attacks.

Other websites, including the Muslim Brotherhood and the Palestinian Islamic Jihad, referred to bin Laden's "martyrdom."

Hamas and the Fatah are scheduled to sign their new unity agreement this week in Cairo.

Officials with the Muslim Brotherhood, which hopes to rise to power in a successive Egyptian government, said bin Laden's death removes the need for U.S. troops in Iraq and Afghanistan.

"It is time for Obama to pull out of Afghanistan and Iraq and end the occupation of U.S. and Western forces around the world that have for so long harmed Muslim countries," Essam al-Erian, a member of the Muslim Brotherhood's governing body, told Reuters.

Updated 3:27 p.m.

The Jerusalem Post's Khaled Abu Toameh reports that a second Hamas official, Ismail al-Ashqar, said his organization disagreed with bin Laden on some issues, but not all.

"We consider Osama bin Laden a modest man and a mujahed," Ashqar said. "He had billions of dollars and yet he give all that up and chose to fight alongside his Afghan brothers against the Soviet Union. He considered America as the enemy of Islam and Muslims because of the harm it did to Muslims."