BAGHDAD, Iraq - A car bomb exploded outside a police academy south of Baghdad during a graduation ceremony today, killing at least 20 people amid a surge in violence ahead of a landmark election. Hours earlier, another car bomb killed two Iraqis in the nation's capital.

The bloodshed brought the death toll to more than 90 in the last four days. Despite the insurgency - which U.S. troops and Iraqi security forces have been helpless to prevent - American and Iraqi leaders insist the vote would go forward as scheduled despite the violence aimed against holding the ballot.

"We will not allow the terrorists to stop the political process in Iraq," Iraqi Interim Prime Minister Ayad Allawi, a secular Shiite leader, said today. "The elections process is the basis for the deepening of the national unity in Iraq."

The explosion outside a gate of the police academy in Hillah, about 60 miles south of Baghdad, was the latest in a string of attacks against Iraqi security forces. Capt. Hady Hatef said it killed at least 20 people and wounded unspecified number.

The number of Iraqi policemen killed in the last four months of 2004 was 1,300 before the latest blast, according to the Iraqi Interior Ministry figures released today. It was unclear if all the 20 killed were police.

The Iraqi police and security troops represent a soft target for the insurgents because of their poor training and equipment compared to the U.S.-led coalition forces. The militants consider Iraqi soldiers as collaborators with the American occupiers.

"Hostile forces are still trying to harm and cause damages, but the Iraqi forces are becoming better and they have captured and killed some terrorists," Allawi told reporters.

He said that the Iraqi security forces recently arrested two aides of Jordanian terrorist Abu Musab al-Zarqawi who is believed to be leading the insurgency in Iraq.

"They were detained in Mosul along with three or four others and they have started confessing now to Iraqi security about the networks they run in order to harm our people," Allawi said.

Earlier today, an explosives-filled car following a convoy of U.S. and Iraqi troops detonated in Baghdad's western district of Amiriyah, killing two Iraqi civilians and wounding 10, police officials said. No troops were hurt.

The attack also came as a funeral procession was held nearby for slain Baghdad governor Ali al-Haidari, who was known for cooperating closely with U.S. troops. Al-Haidari was killed on Tuesday. It was not clear if Wednesday suicide car bomb was targeting the mourners, which included Iraqi officials, or the convoy of troops.

In a third attack today, gunmen killed Iraqi police Col. Khalifa Hassan and his driver as they headed to work in the restive city of Baqoubah, 30 miles northeast of Baghdad, Dr. Ahmed Fouad of the Baqoubah General Hospital said.

Also, four Iraqi civilians were killed and two others were injured when U.S. soldiers opened fire after their convoy was attacked by rocket-propelled grenades in central Ramadi, 60 miles west of Baghdad, according to Dr. Riyad al-Hiti of the Ramadi hospital. The U.S. military had no immediate information about the incident.