BAGHDAD - A truck packed with rockets blew up yesterday in a Shiite area of Baghdad, killing 18 people in the deadliest single blast in the city in more than three months. North of the capital, three U.S. soldiers were killed by gunfire.

A U.S. military spokesman said the blast appeared to have been an accident that occurred as Shiite militiamen were transporting the weapons through a densely populated neighborhood of northern Baghdad - possibly to fire at a nearby American base.

Iraqi police said a suicide truck bomber had targeted the house of an Iraqi police general, who was not at home but whose nephew was among those killed. U.S. officials said 75 people were wounded, and police said they included the general's elderly parents.

The U.S. military disputed the police account, saying Shiite extremists were transporting rockets and mortars on a tractor-trailer when the weapons mistakenly exploded. Witnesses also confirmed the vehicle was carrying weapons.

"They were trying to attack us . . . and it went off," said a U.S. military spokesman, Lt. Col. Steve Stover, who provided the death toll. "They wouldn't waste rockets like that" on a suicide attack.

It was the deadliest single explosion in Baghdad since March 3, when a suicide car bomber killed 22 people in eastern Baghdad. Sixteen people died in a mortar attack in the Shiite militia stronghold of Sadr City on April 9.

Yesterday's carnage was a grim reminder of the bombs and killings that rocked the capital before President Bush rushed about 30,000 reinforcements to Iraq last year to curb a wave of Shiite-Sunni slaughter.

More recently, violence has dropped sharply since a May 11 cease-fire ended seven weeks of fighting between U.S. and Iraqi soldiers and Shiite militiamen in the capital's Sadr City district.

Nevertheless, a car bomb exploded last night in the Shiite district of Karradah in east Baghdad, killing seven people, including three policemen, and wounding 11 people, according to police and hospital sources who spoke on condition of anonymity because they were not supposed to release the information.

The three American soldiers died when gunmen opened fire on them near the town of Hawija, 150 miles north of Baghdad, a U.S military statement said. No further details were released.

Their deaths brought to at least 4,090 the number of American military personnel who have died in the Iraq war since it began in March 2003, according to an Associated Press count.

Hawija, once a hub for Sunni militants and disaffected allies of Saddam Hussein, was believed to have been pacified in recent months. Last year the town was the scene of one of the largest ceremonies where tribal sheikhs joined forces with the Americans to fight al-Qaeda in Iraq.

Marine Officer Acquitted of Haditha Cover-Up

A military jury

yesterday acquitted a Marine intelligence officer of charges that he tried to help cover up the killings of 24 Iraqis, including women and children.

Cheers erupted

as the seven-officer panel

at Camp Pendleton, Calif., cleared First

Lt. Andrew Grayson of Springboro,

Ohio, the first of three Marines to be tried in the biggest U.S. criminal case involving Iraqi deaths linked to the war. The verdict came after five hours of deliberations.

Grayson, who has always

maintained he did nothing wrong, was not at the scene of the killings in Haditha on Nov. 19, 2005. He was accused of telling a sergeant to delete photos of the dead from a digital camera and laptop. He was acquitted of two counts of making false official statements, two of trying to fraudulently separate from service, and one of attempt to deceive by making false statements.

The killings occurred

after a roadside bomb killed one Marine and wounded two.

Four enlisted Marines

initially were charged with murder, and four officers were charged with failing to investigate the deaths. Charges were dropped against

five of the Marines but remained against Grayson, Staff Sgt. Frank Wuterich, and

Lt. Col. Jeffrey Chessani, who was the battalion commander.

Wuterich and Chessani

still face court-martial.

- Associated Press