The bloodshed raised the death toll from insurgent attacks to more than 90 in the past four days. Despite the insurgency -- which U.S. troops and Iraqi security forces have been helpless to prevent -- U.S. and Iraqi leaders insist the vote will 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 Wednesday. "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 an unspecified number.

Polish Lt. Col. Artur Domanski, a spokesman for the multinational forces in Hillah, said at least 10 policemen were killed and 41 others were injured in the suicide attack.

"I'm afraid that this number can increase," he said.

In Baqoubah, 30 miles northeast of Baghdad, a suicide attacker rammed his car into a joint police and Iraqi National Guards checkpoint, killing five policemen and wounding eight other Iraqis, U.S. military spokesman Maj. Neal O'Brien said. The vehicle's driver also was killed.

"The Iraqi police and Iraqi National Guard have exerted more control over security in Baqoubah, making them an obstacle to the anti-Iraqi forces' attempts to disrupt the upcoming elections," O'Brien said.

The number of Iraqi policemen killed in the last four months of 2004 was at least 1,300, according to Iraqi Interior Ministry figures released Wednesday.

The Iraqi police and security troops represent a soft target for the insurgents because of their poor training and equipment compared with U.S.-led coalition forces. The militants consider Iraqi soldiers to be 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 the Iraqi security forces recently arrested two aides of Jordanian 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 Wednesday, 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 Gov. Ali al-Haidari, who was known for cooperating closely with U.S. troops. Al-Haidari was killed Tuesday. It was unclear whether Wednesday's suicide car bomb was targeting the mourners, which included Iraqi officials, or the convoy of troops.

The Ansar al-Sunnah Army, a radical Islamic group with terrorist credentials, claimed responsibility for the attack. A statement posted on the Internet said the attack was a "martyrdom" operation. The authenticity of the claim could not be verified.

In a third attack Wednesday, gunmen killed Iraqi police Col. Khalifa Hassan and his driver as they headed to work in Baqoubah, 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.

A U.S. soldier belonging to Task Force Olympia was killed and two were wounded after their patrol was attacked with small arms and rocket-propelled grenade fire Tuesday afternoon in Tal Afar in northern Iraq, the U.S. military said Wednesday.

Five other U.S. servicemen died in three separate attacks Tuesday, making it the deadliest day for the U.S. military in Iraq since the Dec. 21 suicide bombing at a mess tent in Mosul, an attack that killed 22 people -- including 14 U.S. soldiers and three American contractors.

White House spokesman Scott McClellan on Tuesday acknowledged security "challenges" in Iraq but said the election timetable would not be changed.

Prime Minister Tony Blair said Wednesday he remains committed to holding elections as scheduled.

"I am committed to it, yes, because I think it is extremely important that the terrorists don't gain a victory," Blair told British Broadcasting Corp. radio. "The vast majority of Iraqis want to participate in these elections."

Many areas of Iraq are calm, but vast regions, including the capital, are extremely dangerous. In places like Fallujah, which was bombed to ruins in a U.S.-led campaign in November, and the northern city of Mosul, there has been little headway in preparing for the vote.

The attacks have prompted Sunni Arab clerics to call for a boycott, and Iraq's largest Sunni political party announced it was pulling out of the race because of poor security.

The country's Shiites, many of whom are in the government, want to take power but they also want the Sunnis to participate in the vote. A low turnout because of the fear of violence or a Sunni boycott could undermine the legitimacy of the country's first free elections since 1958.