However, the foreign hostage crisis has deepened with the abduction of a Japanese security contractor in Iraq.
Aljazeera and agencies quoted US forces as saying on Monday they had killed 75 rebels in a sweep near the Syrian border for Iraq's most wanted man.
The US military said a joint air and ground operation had been
launched in western Iraq to eliminate "terrorists and foreign
fighters" from an area "known as a smuggling route and sanctuary for foreign fighters", north of the Euphrates river.
But Abu Musab al-Zarqawi's group immediately denied that 75 had been killed and also denied any of its leaders had been arrested, in internet statements posted on Monday, contradicting reports from Iraqi officials that two senior members had been detained.
Also on Monday, al-Qaida-linked Army of Ansar al-Sunna released identity card copies giving the captive's name as Akihiko Saito, 44, and said he had been captured during a fierce battle in western Iraq.
Japanese Foreign Minister Nobutaka Machimura confirmed that a Japanese employee of a foreign security firm had been seized, Kyodo News reported, while a Cypriot security firm confirmed Saito was on its payroll.
There is no let-up in the wave of
violence convulsing the country
The statement said Saito was captured during an ambush of a convoy leaving a US base west of Baghdad during which several other foreigners were killed and Saito seriously wounded.
"When the American helicopters arrived, the mujahidin captured and killed [their hostages], except for one of them, a Japanese, currently detained by the mujahidin but whose wounds are serious.
"We will publish photographs of those who were killed," it said.
The Army of Ansar al-Sunna has carried out murders of foreign hostages in the past, often releasing video footage of the killings on websites.
Three US marines and a soldier were killed in clashes in Iraq, the military said on Monday.
The three marines were killed in the northwest part of al-Anbar province where the US military launched an offensive late on Saturday against anti-US fighters.
Two of the marines were killed by gunfire in the city of Qaim near Iraq's western border with Syria, the military said. One was killed on Sunday and another was killed on Monday.
Mass executions are taking place
with troubling regularity in Iraq
The third marine died on Sunday of bullet wounds inflicted in the town of Obaidi, also near the country's western border about 300km west of Baghdad, the military said.
The fourth service member, a soldier assigned to One Task Force Liberty, was killed on Sunday by gunfire near Samarra, 95km north of Baghdad, the military said.
The three marines were assigned to Regimental Combat Team 2, 2nd Marine Division, II Marine Expeditionary Force. The names of the deceased marines and soldier were withheld pending notification of next of kin.
Meanwhile, the family of Australian hostage Douglas Wood pleaded publicly with his captors for him to be given emergency blood pressure, cholesterol and heart medicines.
The plea came just hours before the expiry of a deadline set by his captors for Canberra to announce it was withdrawing its forces from the US-led forces in Iraq.
Australia, which has 550 soldiers already stationed in Iraq and is sending 350 more, has rejected the captors' demands.
US forces said recently they nearly captured al-Zarqawi on 20 February when he just had time to jump out of a vehicle travelling between Hiyt and Haditha in the Euphrates valley.
A Japanese passport with Saito's
name on Ansar al-Sunna website
US forces did not say if they sustained any casualties in the desert sweep, but the military earlier said it lost eight soldiers over the weekend elsewhere in Iraq.
Amid the violence, Iraq's new government held its second meeting, a day after parliament approved the nomination of new ministers for the key portfolios of oil and defence.
The whole cabinet was sworn in a second time on Monday after Kurdish leaders complained that the text of the oath read by ministers last week had been stripped of a crucial reference to a federal Iraq, as sought by the Kurds.
Iraq's Kurdish president, Jalal Talabani, has said he believes al-Zarqawi's al-Qaida in the Land of Two Rivers has become weak and isolated regardless of the many explosions that have rocked the country in recent weeks.
He said al-Qaida and some countries in the neighbourhood were funding al-Zarqawi's fighters.
In continuing violence, nine Iraqis were killed and 17 wounded, as anti-government fighters continued to strike at the fledgling security forces.
Four people were killed and nine wounded when a bomber rammed his car into two police vehicles at a checkpoint in southwest Baghdad, an Interior Ministry official said.
Al-Zarqawi's group later claimed responsibility for the attack in an internet statement.
Two more people were killed when a parked car exploded in the crowded southern business district of Dura, the official said.
Iraq's cabinet ministers retook
oaths to quell Kurdish anger
In the key northern oil refinery town of Baiji, defence force chief, Lieutenant-Colonel Umar Dalaf al-Qaisy, was shot and killed by assassins, police said.
Further south, in the town of Ishaki, truck driver Sami Nizar Ali was killed in an attack on his convoy.
Just north of the capital, an Iraqi soldier was killed by a roadside bomb targeting a joint US-Iraqi convoy in Shabab village near Dujail, the army said. Four suspects were arrested.
Call for inquiry
Shia spiritual leader Grand Ayat Allah Ali al-Sistani meanwhile called for an investigation into the murder of 14 Sunni Arabs amid accusations they had been killed by Shia in a tit-for-tat killing, Interior Minister Bayan Bakir Sulagh said.
The bodies of the 14 were found on wasteland near the Baghdad Shia district of Sadr City on Friday bearing signs of torture and summary execution.
The bodies of eight more civilians, believed to be Shias from Sadr City, were discovered tortured and then executed south of Baghdad on Monday, in an area where Sunni fighters operate, the Iraqi army and medics said.