BAGHDAD, Iraq – An explosion of insurgent violence killed seven American service members in Iraq over the weekend even as the Shiite-dominated parliament reached out yesterday to Sunni Arabs, approving four more of them to serve as government ministers.

More than 300 people, including American forces, have been killed in a torrent of insurgent attacks since Iraq’s Cabinet was sworn in April 28 with seven positions undecided.

Parliament approved all six of the nominees placed before it yesterday by Prime Minister al-Jaafari. But one of the four Sunnis, the man tapped as human rights minister, rejected the post on the grounds of tokenism, tarnishing the Shiite premier’s bid to include the disaffected minority believed to be driving Iraq’s deadly insurgency.

Once that position is filled, only one vice premiership will remain open. Mr. al-Jaafari said he hopes to name a woman to that job, filling out a Cabinet after more than three months of political wrangling since the country’s landmark democratic elections.

Three of the American victims were soldiers killed yesterday in bombings in central Iraq, the American command said. One soldier was killed and a second was wounded during an attack on a patrol near Samarra, 60 miles north of Baghdad. Two others died in an explosion near Khaldiyah, 75 miles west of Baghdad, the military said.

On Saturday, three Marines and a sailor were killed in fighting with insurgents in western Iraq, some of whom fought from inside a hospital, the military said. The battle, in which an unspecified number of insurgents were killed, began in Haditha, 140 miles northwest of Baghdad, when American forces responding to small arms fire near the Haditha Dam saw Iraqi civilians running from Haditha Hospital, the military said.

The soldiers were then attacked by a suicide car bomb that destroyed a nearby building and set fire to the hospital. Insurgents inside the hospital set off a roadside bomb and fired small arms and rocket-propelled grenades at the American forces.

After the fight, Marines searched the hospital and found fortified firing positions with sandbagged windows.

At least 1,599 members of the American military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

American and Iraqi forces hit back over the weekend, capturing 109 suspected insurgents and killing six in a series of raids, the American military said. Among those captured was an unidentified senior military officer in Saddam’s government.

The spiking violence – including roadside bombs and suicide attacks – has raised concern in Washington, where Senator Levin, a Michigan Democrat and member of the Senate Armed Services Committee, said only a quarter of the 168,000 Iraqi forces being trained and equipped by the American-led coalition “are able and willing to take on the insurgents.” Political infighting presented as big a challenge, he told ABC’s “This Week” TV program.

Mr. Levin said if Iraqis fail to write a constitution, elect a new government, and develop reliable security forces by early next year, Washington will have to rethink its commitment to Iraq. Senator Hagel, a Nebraska Republican and member of the Senate Foreign Relations Committee, agreed.

Iraqi politicians spent the first three months after historic elections January 30 trying to form a Cabinet, but Mr. al-Jaafari argued yesterday the delay was necessary to ensure those selected had broad support.

“The need to represent all sectors of Iraq was the reason for the delay,” he told reporters after the parliament vote. “Time was not spent in vain.”

Less than half of parliament – 112 of the 115 lawmakers present – approved Mr. al-Jaafari’s nominations. The poor showing underscored the persistent ethnic and religious tensions that have hampered the new government.