More than 40 rockets were fired by Palestinian terrorists in Gaza into Southern Israel Monday, the fourth straight day of attacks targeting civilian areas. In all, more than Israeli military officials say, more than 200 rockets have been fired since Friday, placing more than 1 million people at risk.

Retaliatory Israeli airstrikes reportedly have killed about 20 people.

The good news is that Israel's "Iron Dome" missile defense system "aced its first serious test" by knocking down a majority of the incoming rockets targeted. The system uses radar to identify missiles which are most likely to land in populated areas.

Dozens of missiles fired from Gaza have been intercepted. Videos showing several examples can be seen here.

Analysts say the success rate would be challenged by greater volume. Most of the rockets fired this week are believed to come from the Palestinian Islamic Jihad and the Palestinian Resistance Committees. An Islamic Jihad official indicated it might escalate the conflict, saying it might unleash "fire and destruction."

"Islamic Jihad is frustrated by its inability to inflict real damage on Israelis while the IDF has dealt a significant blow to terrorist organizations in the Gaza Strip and their weapons storage facilities," Brig.-Gen. Yoav Mordechai told Army Radio Monday night.

Israeli defense officials say the Islamic Jihad is doing Iran's bidding by firing the rockets. Should things escalate, they say they have plans to take more aggressive action to stop the attacks.

Three Iron Dome batteries are in place in southern Israel. Officials hope to activate 13 throughout the country for more protection and are developing similar systems for longer-range missiles.