BAGHDAD (AP) – In one of the deadliest attacks on American ground forces since the Iraq war started more than four years ago, a suicide car bomber struck a patrol base northeast of Baghdad and killed nine American soldiers and wounded 20, officials said.

An Iraqi civilian also was wounded in the attack on Task Force Lightning soldiers in Diyala province, a volatile area that has been the site of fierce fighting involving American and Iraqi troops, Sunni insurgents and Shiite militias.

At least 48 Iraqis were killed in seven other bombings, violence that has persisted despite a nearly 10-week-old American-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 an American base north of Baghdad in just over two months and was notable for its use of a suicide car bomber. Militants have mostly used hit-and-run ambushes, roadside bombs or mortars on U.S. troops and stayed away from direct assaults on fortified military compounds to avoid American firepower.

On Feb. 19, insurgents struck an American combat post in Tarmiyah, about 30 miles 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.

American troops are facing increasing danger as they step up their presence in outposts and police stations in the Baghdad area as part of the security crackdown to which President 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Sunni militants are believed to have withdrawn to surrounding areas such as Diyala province where they have safe haven.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 American command also deployed an extra 700 soldiers to the area last month.

An American soldier also was killed Monday in a roadside bombing in Muqdadiyah, about 60 miles north of Baghdad, a predominantly Shiite area that also is in Diyala, 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.

The deaths raised to 85 the number of U.S. 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 Dec. 1, 2005, when a roadside bomb killed 10 Marines and wounded 11 on a foot patrol near Fallujah.

Twelve soldiers died when a Black Hawk helicopter crashed in Diyala on Jan. 20. The military said it might have been shot down but the investigation is still ongoing.

In other devastating attacks, 14 Marines were killed when a roadside bomb struck an amphibious assault vehicle near the western town of Haditha on Aug. 3, 2005. And a suicide bomber struck a mess tent in a base near Mosul on Dec. 21, 2004, killing 22 people, including 14 American soldiers and three American contractors.

On Tuesday, two car bombs exploded near the Iranian Embassy in Baghdad, police said. The bombs exploded within two minutes of each other at about 10 a.m. in a public parking lot located about 150 yards from the front of the Iranian Embassy, wounding six civilians but causing no damage to the embassy or its guards, a police officer said on condition of anonymity out of concern for his own security.

On Monday, two parked car bombs exploded outside the Iranian Embassy. One bomb exploded near the same public parking lot, killing one civilian and wounding another; the other parked car bomb exploded close to a police patrol near the Iranian Embassy, killing one civilian and wounding two officers, police said.

The prominent Iraqi Sunni insurgent group Islamic Ansar al-Sunnah issued a statement on its Web site claiming responsibility for Monday’s bombing near the parking lot.

At least 68 Iraqis were killed or found dead Monday, according to police, including 10 in a suicide car bombing against a police station in the Diyala provincial capital of Baqouba.

With the American casualty toll mounting, Democratic leaders in Washington agreed Monday on legislation that requires the first American combat troops to be withdrawn from Iraq by Oct. 1 with a goal of a complete pullout six months later. Bush has promised to veto any such measure as the legislative confrontation intensifies.