Five US soldiers were among seven people killed by a suicide bomber in the Iraqi city of Mosul, the US military says.
The blast happened when a bomber drove a truck laden with explosives into a police station in the northern city.
Two Iraqi policemen were killed and 20 others hurt, the US said. Iraqi reports said as many as 70 people were hurt.
US and Iraqi officials describe Mosul as al-Qaeda in Iraq's last major urban stronghold in the country.
Most of the country has seen a considerable improvement in security in the last year, reports the BBC's Jim Muir, in Baghdad.
But Mosul is one place where insurgents have defied US and Iraqi government efforts to restore control.
This is the largest number of US troops to die in a single incident for months, our correspondent adds.
Reports said the bomber made a sharp turn as he neared the station and charged the truck through an iron fence, careering into a sandbagged wall beyond.
Two people suspected of involvement in the attack had been detained, the US military said.
US combat troops are due to pull out from Iraq's cities by the end of June.
Under a recent agreement, they are expected to remain elsewhere in the country until the end of August 2010.
US President Barack Obama says he wants all US troops out of Iraq by the end of 2011.