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 horrific 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 in an interview 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 volatile 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 angry, impoverished city where efforts to obliterate al-Qaida and other Sunni militants have failed over the years. About 5,000 U.S. troops and 36,000 Iraqi army and police officers currently are believed to be stationed in Mosul and the surrounding province.

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.