Nigerian Islamist fighters have returned from training in Somalia with the militant organization al-Shabaab - a group which has received al-Qaida training.

"We want to make it known that our jihadists have arrived in Nigeria from Somalia where they received real training on warfare from our brethren who made that country ungovernable," the Nigerian Islamist sect Boko Haram said in a written statement.

Boko Haram vowed to wage jihad soon, specifically in northern Nigeria and in the capital of Abuja. "This time round, our attacks will be fiercer and wider than they have been," the statement said.

Boko Haram militants have already used their new training to follow through on such threats. A suicide bomber drove an explosive-laden car through a police station in Abuja Thursday, killing himself and a traffic warden.

A high ranking al-Shabaab leader revealed in May that al-Qaida helped train his group's fighters to overthrow the Somali government. Sheikh Mukhtar Rabow, a.k.a. Abu Mansur, said that Osama bin Laden sent fighters to Somalia in the 1990s in order to train the Somali guerrillas.

The Somali government collapsed in 1991. Al-Shabaab, which emerged out of several pre-existing Islamist groups, has been battling the Somali Transitional Federal Government (TFG) for control of the country since 2004. Mansur added that al-Shabaab has continually relied on al-Qaida for military and financial support.

Al-Shabaab has openly expressed its support for al-Qaida. The group has pledged allegiance to Osama bin Laden and vowed to avenge his death after U.S. Navy SEALs shot and killed him in his Abbottabad compound.