Multi-national security forces have captured a key associate of Iraq's most wanted terrorist, Abu Musab al-Zarqawi (search), FOX News has confirmed.

The man was identified as Ammar Adnan Mohammed Hamza al-Zubaydi, also known as Abul Abbas.

Al-Zubaydi is accused of planning an April 2 assault by dozens of insurgents who blew up car bombs and fired rocket-propelled grenades outside Abu Ghraib (search) prison, an Iraqi government statement said.

The statement said al-Zubaydi was captured three days ago in Baghdad.

Al Qaeda in Iraq (search), the Usama bin Laden-allied terror group run by al-Zarqawi, is responsible for numerous beheadings and terrorist bombings across the country.

Meanwhile, an explosion of insurgent violence killed seven U.S. service members in Iraq over the weekend even as the Shiite-dominated parliament approved four more Sunni Arabs to serve as government ministers.

One of the four Sunnis 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.

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

Parliament approved all six of the nominees placed before it Sunday by Prime Minister Ibrahim al-Jaafari.

The position of human rights minister was rejected by its nominee, but once it is filled, only one vice premiership will remain open. 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 U.S. victims were soldiers killed Sunday in bombings in central Iraq, the U.S. command said. One soldier was killed during an attack on a patrol near Samarra, 60 miles north of Baghdad. The other two died in an explosion near Khaldiyah, 75 miles west of Baghdad, the military said.

On Saturday, three U.S. 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 was killed, began in Haditha, 140 miles northwest of Baghdad, when U.S. forces responding to small arms fire near the Haditha Dam and saw Iraqi civilians running from Haditha Hospital, the military said.

The soldiers were then attacked by with a 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 U.S. forces.

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

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

U.S. and Iraqi forces hit back in recent days, capturing dozens of suspected insurgents and killing six in a series of raids, the U.S. 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 Sen. Carl 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 U.S.-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.

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.

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

"Time was not spent in vain," he said after the parliament vote.

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

When complete, the government was to include 17 Shiite ministers, eight Kurds, six Sunnis and a Christian. Three deputy premiers also have been named — one each for the Shiites, Sunnis and Kurds, with the fourth held open for a woman.

The defense ministry went to Saadoun al-Duleimi, a former lieutenant colonel in Saddam Hussein's General Security Directorate who left Iraq in 1984 and lived in exile in Saudi Arabia until Saddam's fall in April 2003. A moderate, he comes from a powerful Sunni tribe in Anbar province, the homeland of the insurgency.

The oil ministry was returned to Ibrahim al-Uloum, a Shiite who was accused of inexperience when he held the post in the first U.S.-picked Cabinet formed in the early months after the American-led invasion toppled Saddam.

Hashim Abdul-Rahman al-Shibli said he could not accept his appointment as human rights minister, which would have brought the total number of Sunnis in the Cabinet to seven.

"Concentrating on sectarian identities leads to divisions in the society and state, and for that reason I respectfully decline the post," al-Shibli said at a news conference.

The Kurdish environment minister, Narmin Othman, will act as human rights minister until a replacement is found, al-Jaafari's aides said.

Al-Jaafari pledged Sunday to take "all necessary measures" to restore security and said the government could impose martial law, if necessary.

The parliamentary vote came a day after two explosives-laden cars plowed into an American security company convoy in Baghdad, killing at least 22 people — including two Americans. At least 36 Iraqis, three Americans, an Australian and an Icelander were injured in the attack, the U.S. Embassy said.

The two dead Americans were employed by CTU Consulting, a Fayetteville, N.C.-based security consultancy. The company identified them as Brandon Thomas and Todd Venette. Venette was from Russellville, Ark., his friends and family said; the company did not give Thomas' hometown.

Al Qaeda in Iraq claimed responsibility for the attack, saying it detonated a booby-trapped car as a "convoy of CIA passed," according to a statement posted Sunday on a militant Web site. The authenticity of the claim could not be verified.

In other violence Sunday:

— Four Iraqis were killed in two roadside bombings and gunfire in Mosul, 225 miles northwest of Baghdad, the U.S. military said. One insurgent was also killed and another wounded in a clash with a U.S.-Iraqi patrol.

— Gunmen shot and killed Zoba Yass, a senior official in Iraq's Transportation Ministry, and his driver in southern Baghdad, police and transportation officials said.

The Associated Press contributed to this report.