(Updates with three American soldiers killed) By Ibon Villelabeitia BAGHDAD, Feb 19 (Reuters) - Iraqi insurgents, using a suicide bomber to explode a fuel tanker, launched one of their biggest assaults in months on a joint U.S. and Iraqi outpost on Monday, killing two U.S. soldiers and wounding 17 others. The attack, north of Baghdad, was part of a day of bombings and shootings by militants as tens of thousands of U.S. and Iraqi forces fanned out in the capital in a new operation to crack down on rampant sectarian violence. Three U.S. soldiers were killed and two others wounded in a roadside bomb blast southwest of Baghdad, the U.S. military said. More than 40 Iraqis were killed, including 10 in bombings in Baghdad, in other attacks. Near Falluja in the west, 13 members of a single family were shot dead by suspected al Qaeda militants while in nearby Ramadi two suicide bombers killed 11 people in an attack on the home of a tribal leader who had opposed al Qaeda. Iraqi police said a suicide bomber at the wheel of a fuel tanker blew himself up as U.S. forces entered an Iraqi police station in the town of Tarmiya, which U.S. troops use as an outpost. The self-styled Islamic State in Iraq, an al Qaeda-linked group, claimed responsibility for the attack via a Web statement. The town is a Sunni Arab insurgent stronghold some 40 km (25 miles) north of Baghdad in the notoriously violent province of Salahaddin. U.S. military helicopters hovered over the area transporting the wounded after the blast, which almost demolished the police station. A U.S. military spokesman in Baghdad declined to provide more specific information on the attack, a rare coordinated assault on a U.S. base. "It was not just a spontaneous attack. It wasn't just people taking potshots at us," Major Steven Lamb told Reuters. A U.S. military statement said U.S. soldiers secured the area and evacuated the wounded. It was not known if any insurgents were killed. More than 3,100 U.S. soldiers have been killed in Iraq since the U.S.-led invasion in 2003. The violence by militants came a day after two bombs killed 60 people in a Shi'ite market area in Baghdad in the bloodiest assault since the new crackdown by U.S. and Iraqi forces began on Wednesday. U.S. military officials have warned that militants could strike in areas outside Baghdad while U.S. and Iraqi forces focus their efforts inside the capital to end sectarian violence that authorities fear could lead to all-out civil war. The bombings in the capital that killed 10 people underscored the challenge of stabilising the city that is the epicentre of Iraq's bloodletting. FAMILY AMBUSH Violence also flared to the north and west of the capital, leaving more than 20 people dead including the 13 near Falluja who were returning from a funeral. In that attack, suspected al Qaeda militants pulled the family of mourners from a minibus and gunned them down, including two young boys, after finding out they were from a Sunni tribe opposed to al Qaeda, police said. The western city of Falluja is in the Sunni Arab insurgent bastion of Anbar province. Among the Baghdad attacks, four people died when a bomb tore through a minibus in Karrada, a mostly Shi'ite area where Christians also live. A Reuters photographer saw charred bodies lying on the street after the blast blew off the top of the bus. Shi'ite Prime Minister Nuri al-Maliki, under pressure from Washington to rein in violence, had trumpeted the crackdown as a "brilliant success". More than 110,000 Iraqi and U.S security forces are taking part in Operation Imposing Law, aimed at curbing sectarian violence by Sunni insurgents and Shi'ite militias. The campaign does appear to have sharply reduced the number of killings by death squads in Baghdad, from 40-50 a day, to three reported on Monday. But U.S. generals, mindful of similar crackdowns last year that failed, have been more cautious and have warned that militants were adapting their tactics. (Additional reporting by Dean Yates, Ahmed Rasheed and Majid Hameed in Baghdad)
