In Baghdad, Iraqi troops thwarted an attack by three suicide bombers outside the heavily fortified Green Zone. Although several people were wounded, the U.S. military calls Thursday morning's attack a failure for the insurgency.

Shortly before 9 a.m., a suicide car bomber detonated his bomb at a checkpoint near an entrance to the Green Zone, an extensive walled-off area in central Baghdad that houses coalition and Iraqi government officials.

The U.S. military's top spokesman in Iraq, Brigadier General Donald Alston, said Iraqi troops at the checkpoint had performed superbly. "Today Iraqi security forces dealt terrorists another significant blow, defeating an attack in the vicinity of Checkpoint 2," he said.

General Alston said alert soldiers knew something was wrong before the car bomber reached them.  "The troops that were at the checkpoint identified the vehicle as a threat, engaged the vehicle, and caused it to detonate several yards short of the checkpoint," he said.

Two men on foot, who turned out to be wearing explosive vests, then ran toward the checkpoint, but were promptly engaged by the Iraqi security forces.

One would-be attacker was killed when the explosives he was wearing went off prematurely, and the other was disabled before he could detonate the device he was wearing. He was disarmed, arrested and hospitalized with a leg wound.

Police said the vehicle blast was followed by a mortar attack. However, the apparently coordinated assault appears to have killed no one except two of the attackers.

Suicide bombs have been nearly a daily occurrence in the capital and other parts of the country since the announcement of Iraq's elected government on April 28.

The U.S. military said 23 car bombs, including six suicide car bombs, went off throughout Iraq last week.

General Alston said this was the lowest number in the the past 11 weeks. He added that foot-borne suicide bombs account for a lower proportion of suicide attacks.

According to the Associated Press, violent deaths among Iraqi civilians far exceeded those of soldiers or police during the first six months of this year, based on figures compiled from Iraqi government ministries.

Suicide bombings are thought to be mostly carried out by non-Iraqis, although they are probably Sunni Arabs with ethnic and sectarian links to homegrown Iraqi insurgents.

Also Thursday, the U.S. military announced the capture of two key members of al-Qaida in Iraq, the organization belived to be responsible for most suicide attacks.

One of the men is suspected in the kidnapping and murder of an Egyptian envoy, and in attacks on diplomats from Pakistan and Bahrain.

Khamis Farhan Khalaf Abd al-Fahdawi, known as Abu Seba, was arrested last Saturday following operations near Ramadi, west of Baghdad.

Another al-Qaida lieutenant in Iraq, Abdullah Ibrahim Mohammed Hassan al Shadad, also known as Abu Abdul Aziz, was reportedly captured Sunday.