A suicide car bomb struck a patrol base northeast of Baghdad, killing nine US soldiers and wounding 20 in the single deadliest attack on American ground forces in more than a year, the military said Tuesday. An Iraqi civilian also was wounded in Monday's attack on Task Force Lightning soldiers in Diyala province, a volatile area that has been the site of fierce fighting involving US and Iraqi troops, Sunni insurgents and Shi'ite militias. At least 48 Iraqis were killed in seven other bombings, violence that has persisted despite a nearly 10-week-old US-Iraqi security crackdown aimed at pacifying Baghdad. Of the 20 wounded in the attack on the patrol base, 15 soldiers were treated and returned to duty while five others and the Iraqi were evacuated to a medical facility for further care, the military said. It was the second bold attack against a US base north of Baghdad in just over two months and was notable for its use of a suicide car bomber. On February 19, insurgents struck a US combat post in Tarmiyah, about 50 kilometers north of Baghdad, killing two soldiers and wounding 17 in what the military called a "coordinated attack." It began with a suicide car bombing followed by gunfire on soldiers pinned down in a former Iraqi police station where fuel storage tanks were set ablaze by the blast. Militants have mostly used hit-and-run ambushes, roadside bombs or mortars on US troops and stayed away from direct assaults on fortified military compounds to avoid US firepower. American troops are facing increasing danger as they step up their presence in the Baghdad area as part of the security crackdown to which US President George W. Bush has committed an extra 30,000 troops. Sunni militants are believed to have withdrawn to surrounding areas such as Diyala province where they have safe haven. The US command also deployed an extra 700 soldiers to the area last month. The deaths raised to 85 the number of US service members who died have in Iraq in April, making it the deadliest month for American troops since December, when 112 died. It was the single deadliest attack on ground forces since December 1, 2005, when a roadside bomb killed 10 Marines and wounded 11 on a foot patrol near Fallujah. A US soldier also was killed Monday in a roadside bombing in Muqdadiyah, about 60 miles north of Baghdad, the military said in an earlier statement. A British soldier was shot to death while on patrol in the southern city of Basra, officials said. A suicide car bombing also struck a police station in the Diyala provincial capital of Baqouba, killing 10 people and wounding 23. In all, at least 68 Iraqis were killed or found dead in Iraq, according to police, including 19 who died when a suicide car bomber struck near a restaurant outside Ramadi.