Scene at the market after five civilians were killed in Amara

The terror group Al-Qaida in Iraq has vowed to carry out large scale attacks following the killing of its leader, Abu Musab al-Zarqawi, in a U.S. airstrike last week.

The group says in an Internet statement that its future attacks will "shake the enemy like an earthquake and rattle them out of sleep."

The U.S. military commander in Iraq, General George Casey, told Fox News Sunday U.S. forces will be prepared for more attacks. He added that al-Qaida in Iraq is experiencing a vulnerable period now that its leader has been killed.

In other developments, Iraqi police say five Iraqis were killed as British soldiers and insurgents clashed in the southern city of al-Amara. Authorities say the soldiers came under attack early Sunday after entering the city to search for insurgents who fired rockets at a British military base.

Separately, Iran said Sunday it was happy about the death of Zarqawi. A spokesman, Hamid Reza Asefi, also said Tehran did not provide any intelligence to the United States about Zarqawi.

The Jordanian-born militant was said to have personally taken part in beheadings of hostages and other killings.

In other developments, Iraqi police say five Iraqis were killed as British soldiers and insurgents clashed in the southern city of al-Amara.  And a car bomb in Baghdad killed four people.