BAGHDAD -- A suicide truck driver detonated a ton of explosives near a police headquarters in the northern city of Mosul on Friday, killing five American soldiers in the deadliest attack against U.S. troops in more than a year.
The U.S. military said Iraqi police were the bomber's target and that the Americans were caught up as bystanders.
The blast, believed to have been carried out by Sunni extremists, is likely to increase pressure on Iraq's prime minister to ask American combat troops to stay in Mosul after the June 30 deadline for them to pull out of Iraqi cities.
America's top commander suggested this week that even as U.S. troops pull out of other cities, he may have to send reinforcements to Mosul, about 225 miles northwest of Baghdad, and to Diyala province, northeast of the capital.
Of the 31 U.S. troops killed in combat in the Iraq war this year, more than a third -- 11 -- have been in Mosul, an impoverished city where efforts to obliterate al-Qaida and other Sunni militants have failed over the years. About 2,000 U.S. troops and about 20,000 Iraqi army and police currently are stationed inside Mosul.
Besides the five Americans, two Iraqi policemen also died in the midmorning blast Friday near the Iraqi National Police headquarters in the southwest of the city, a U.S. statement said. At least 62 people, including one American soldier and 27 civilians, were wounded, U.S. and Iraqi officials said.
A policeman, who identified himself by his nickname Abu Mohammed, said he saw the truck -- its explosives hidden beneath grain -- driving behind two U.S. Humvees on the street leading to the police headquarters.
The Humvees entered the compound and stopped. Within seconds, the driver rammed through a metal barrier, slammed into a sandbagged wall near the Humvees and triggered the blast as Iraqi guards sprayed the vehicle with gunfire, he said.
Lt. Col. Michael Stuart, chief of operations for northern Iraq, said the target was the police compound and that the patrol just happened to be in the area when the attack occurred.
"It was just bad timing," Stuart told The Associated Press.
Friday's blast was the single deadliest attack on U.S. troops in Iraq since March 10, 2008, when a suicide bomber struck American soldiers on a foot patrol in Baghdad. Five Americans were killed in that attack.
More recently, four U.S. soldiers and their Iraqi interpreter died Feb. 9 in a suicide bombing at a checkpoint in Mosul, Iraq's third largest city with a population of about 2 million. The dead included a lieutenant colonel, one of only three battalion commanders killed in action in the six-year war.
Despite those losses, American casualties have fallen to their lowest levels of the war since thousands of Sunnis abandoned the insurgency and U.S. and Iraqi forces routed Shiite militias in Baghdad and Basra last spring.
But that success has not been replicated in Mosul, where repeated operations have failed to subdue al-Qaida and about a dozen other Sunni militant groups. Many insurgents are believed to have fled to northern Iraq after losing their sanctuaries in Baghdad and elsewhere.
The U.S.-Iraqi security agreement that took effect this year requires American combat troops to leave bases in cities by the end of June. President Barack Obama plans to remove all combat units by September 2010 and withdraw the rest of the U.S. force by 2012.
But the top U.S. commander, Gen. Raymond Odierno, said this week that he worries Iraqi forces won't be ready to assume full responsibility for Mosul by the June deadline.
Odierno told The Times of London in an interview published Thursday that Prime Minister Nouri al-Maliki faces a "very difficult" political decision whether to ask U.S. troops to stay longer in Mosul.
Mosul politicians themselves are divided over the issue. The majority Sunni Arabs generally oppose an extension while minority Kurds and their allies support it. A Sunni party won the provincial election in Mosul last January and is due to take office Sunday now that coalition talks are over.
Atheel al-Nujaifi, who is expected to become governor of the province around Mosul, opposes keeping the Americans in the city.
"There is no reason for U.S. forces to stay beyond June because well-organized and well-disciplined Iraqi security forces are capable of securing the province," al-Nujaifi said Friday. "We will work to ensure this when we take over the provincial council."
However, another prominent local politician, Hashim al-Hamadani, said "the situation in Mosul is grave" and "we need U.S. forces after the June deadline."
"Otherwise, violence will spread," he said.
Also Friday, police in Diyala province said one person was killed and five were wounded when a bomb hidden on a bicycle exploded the night before during a wedding celebration about 45 miles northeast of Baghdad.
Iraqi police in the southern city of Basra said Friday they arrested 65 people in overnight raids after an attack on a U.S. convoy in the area and the kidnapping of two guards working for a local Iraqi security firm.
The arrested included 20 people who were already on a wanted list and 45 others, mostly militiamen, said the city's police spokesman Col. Karim al-Zeidi.
The U.S. military said the American convoy was hit by a roadside bomb near Basra airport on Thursday but there were no casualties. Al-Zeidi said the two company employees were abducted late Thursday. He would not identify the company.
Associated Press writers Chelsea J. Carter and Sameer N. Yacoub, and AP researcher Monika Mathur in New York contributed to this report.