Baghdad, Iraq ? Suicide attackers detonated explosive-laden boats near oil facilities in the Persian Gulf on Saturday, killing two U.S. Navy sailors in a new tactic against Iraq’s vital oil industry. Elsewhere, violence across Iraq killed at least 33 Iraqis and four American soldiers.

It was the first such maritime attack against oil facilities since U.S. troops invaded Iraq more than a year ago. The blasts resembled attacks in 2000 and 2002 — blamed on al-Qaida –against the USS Cole and a French oil tanker off the coast of Yemen that killed 17 American sailors and a tanker crewman.

In the attack, three dhows, or small boats, drew close to two major oil terminals in Gulf waters about 100 miles from Iraq’s main port, Umm Qasr, and exploded when coalition craft tried to intercept them. A U.S. Navy craft was flipped by the blast, killing the American sailors and injuring five others, the U.S. military said.

Initial reports said there was no damage to the terminals, the military said, and Iraq’s main southern oil outlet, Umm Qasr, remained open, a British spokesman said.

Day of violence

The Gulf bombings came on a day of multiple attacks in Iraq: The deadliest was a roadside bomb that hit a bus south of Baghdad, killing at least 13 Iraqis. A mortar barrage struck a crowded market in the capital’s biggest Shiite neighborhood, Sadr City, killing at least seven.

The U.S. soldiers were killed around dawn, when two rockets were fired from a truck and slammed into the base in Taji, 12 miles north of Baghdad, the military said. U.S. helicopter gunships then destroyed the truck. Seven soldiers were wounded, three of them critically, the military said.

Also, an Army reservist missing in Iraq since a convoy attack April 9 was confirmed dead. The remains of Sgt. Elmer Krause, 40, were found Friday, according to a statement Saturday from the Department of Defense. It gave no other details. Another soldier and a U.S. contract worker abducted in the same attack remain unaccounted for.

The latest deaths, along with the combat death of a Marine announced Saturday, brought to 109 the number of U.S. troops killed in Iraq since the beginning of April. The military also announced the death of a soldier in a noncombat incident, bringing to 718 the number servicemembers who have died in the country.

Anywhere from 900 to 1,200 Iraqis have been killed in April, depending on various reports of the death toll from Fallujah.

Maritime oil attacks

British military spokesman Hisham H. Halawi said the port at Umm Qasr, the chief southern outlet for Iraqi oil, remained open after the boat attacks.

The first blast came when a dhow was sighted near the Khawr al-Amaya oil terminal, the Bahrain-based U.S. 5th Fleet said. When an interception team tried to board, the dhow exploded, flipping the U.S. Navy craft.

About 20 minutes later, two more dhows were spotted near the al-Basra oil terminal. They, too, exploded when security teams approached, but there were no casualties among the security teams, the 5th Fleet said.

Halawi said the second dhows were trying to pull close to two tankers at the al-Basra terminal, also known as ABOT.

Insurgents in Iraq have frequently attacked oil pipelines, repeatedly shutting down exports from northern oil fields through Turkey. Southern pipelines, running through relatively more peaceable Shiite regions, have seen fewer attacks.

Iraq is currently producing about 2 million barrels of oil a day, according to the Middle East Economic Survey.

The oil attacks came three days after near simultaneous suicide car bombings in the southern Iraqi city of Basra — 30 miles north of Umm Qasr — that killed 74 people.

Trouble in Fallujah

The violence came as U.S. commanders repeated warnings that they may soon launch a new assault on the besieged city of Fallujah, saying guerrillas had not abided by a call to surrender heavy weapons.

L. Paul Bremer, the top U.S. administrator in Iraq, traveled to the Marine base outside Fallujah for consultations Saturday, while Brig. Gen. Mark Kimmitt told reporters: “Should there not be a good faith effort demonstrated by the belligerents inside Fallujah, the coalition is prepared to act.”

In Saturday’s bloodiest incident, a bomb exploded on a main road as a bus passed near Haswa, 30 miles south of Baghdad. The back of the bus was shredded and seats crumpled. At least 13 people, including a 4-year-old boy, were killed and 17 wounded, said Wasan Nasser, a doctor at Iskan Hospital in neighboring Iskandariyah.

Sadr City

In Sadr City, the capital’s sprawling Shiite slum, angry residents vented anger at Iraq’s U.S. occupiers after the mortar attacks, which followed an early morning clash in the neighborhood between U.S. troops and militiamen loyal to a radical Shiite cleric, Muqtada al-Sadr.

Some of the mortar shells in Saturday’s barrage against Sadr City, which killed at least seven people, hit two miles from any U.S. position — suggesting they may have deliberately targeted civilians in the Shiite neighborhood.

Three shells pounded into the neighborhood’s main souk, known as the Chicken Market, just as morning crowds were gathering to shop. Human flesh could be seen among scattered market stalls and burned-out cars. Craters were blasted out of the asphalt.

At least six Iraqis were killed and 38 wounded, said Yassin Abdel-Qader, a doctor in the area’s Health Directorate. The Baghdad slum is home to more than 1 million people.

Hours later, a projectile struck a two-story house, smashing through its roof and down into the ground floor, tearing a woman to pieces as she took an afternoon nap and wounding her daughter. At least two more landed later in the afternoon, hitting a main street on the edge of Sadr City, breaking windows but causing no casualties.

Before the mortar fire, U.S. troops launched a pre-dawn raid into Sadr City, pursuing al-Sadr militiamen. They caught in a gunbattle in which two Iraqis were killed, according to U.S. Maj. Phil Smith.

During the fighting, a shell pierced the wall of a house, exploding in a bedroom and severely burning a 9-year-old girl and two teenage girls as they slept.

Saddam’s people?

U.S. Army Brig. Gen. Mark Kimmitt suggested former members of Saddam Hussein’s security services were to blame.

“It was clearly an attack on civilians. There was no U.S. military at that spot,” said Lt. Col. James Hutton of the Army’s 1st Cavalry Division, which responded to the attack and helped treat the wounded.

Still, angry Shiites blamed the Americans for the assault. After one of the afternoon strikes, residents chanted, “Long live al-Sadr. America and the Governing Council are infidels.”

In other violence Saturday:

l An Iraqi woman working as a U.S. military translator was shot and killed with her husband as they drove to a U.S. base, a hospital official said.

l A roadside bomb destroyed a car carrying Iraqis near a U.S. base in the northern city of Tikrit, hometown of former Iraqi leader Saddam Hussein and a center for anti-U.S. resistance. Four Iraqis — two police and two civilians — were killed and 16 wounded, the U.S. military said.

l Polish troops clashed overnight with Shiite militiamen in the city of Karbala, killing five, a spokesman for the multinational peacekeeping force in south-central Iraq said Saturday.