Clashes erupted in Haditha on Wednesday, after US and Iraqi troops moved into the Euphrates river city to track down rebels who the military said had escaped an operation earlier this month near the border with Syria.
"Six insurgents were killed in the battle and two marines were reported wounded," the US military said. "Local citizens identified one of the attackers killed as an imam (who) was firing ... an AK-47 assault rifle."
Four more fighters were killed in other clashes in the area, it said, adding that checkpoints have been set up around the city, some 260km northwest of the capital, to prevent fighters fleeing.
The sweep in the northwest of the country came at a time of mounting guerrilla attacks, particularly targeting Iraq's fledgling security forces, and growing US military casualties.
At least nine Iraqis were killed in shootings and bombings on Wednesday, amid a sharp escalation in attacks since the formation of the new government of Prime Minister Ibraham al-Jaafari in early May.
The latest bombing in southern Baghdad late on Wednesday killed three policemen, a Defence Ministry source said.
Officials say more than 600 people have been killed this month alone.
Jordan-born Al-Zarqawi carries a
$25 million bounty on his head
As the sweep of fighters loyal to al-Zarqawi continued in the northwest, Iraqi and US forces said they had arrested two of his top aides and killed another, the day after an internet statement said the Jordanian fugitive linked to al-Qaeda was wounded.
The US military said it had arrested "one of the most wanted people" in northern Iraq, Mullah Kamel al-Assawadi, and one of the regional secretaries of al-Qaeda's frontman in Iraq.
The Iraqi government added that its forces had killed Sabhan Ahmed Ramadan, alias Agha Abu Saad, as he manned a rebel checkpoint in the northern city of Mosul on 19 May.
Ramadan was allegedly the right-hand man of the city's al-Qaeda cell leader, Abu Talha.
US officials gave greater credence on Wednesday to reports that al-Zarqawi was wounded in an ambush with US forces but said they still have not been able to confirm it.
"The assessment is that all these data points may fit together to indicate he has been injured but we can't confirm he has been," a senior US defence official told AFP on condition of anonymity.
Among the data points, he said, are statements by an Iraqi doctor last week that he treated al-Zarqawi, a posting on an Islamist website on Tuesday that said he had been wounded in an ambush, and an internet posting on Wednesday that said he had gone to another country for medical treatment.
"The assessment is
that all these data points may fit together to indicate he has been injured but we can't confirm he has been"
US defence official
The Washington Post quoted an al-Zarqawi lieutenant, identified by his nomme de guerre, Abu Karrar, as saying that the Jordanian fugitive was shot and wounded in fighting near the western city of Ramadi on Saturday and Sunday.
Abu Karrar said aides were helping al-Zarqawi choose someone to replace him as leader of the group if he died, the Post said.
The defence official said there have been a lot of US military operations in western Iraq where he was supposedly wounded.
"It's possible he was injured in one of those," the official said. "It can also be him trying to make a hero out of himself, living to fight another day, quote unquote, proving how resilient he is."
Tuesday's internet posting declaring that al-Zarqawi had been wounded and asking for prayers was on a website used in the past by al-Qaeda in Iraq. It was attributed to the group's information section.
US and Iraqi soldiers patrolling
Baghdad's western suburbs
Iraq's Foreign Minister Hoshyar Zebari meanwhile said he was calling on the United Nations to extend the mandate of the US-led foreign troops stationed in the country, with local forces unable to cope with the onslaught of violence.
Under the terms of Resolution 1546, adopted on 8 June 2004, the UN Security Council said the troop mandate could be re-examined either 12 months after the resolution's adoption, or if the Iraqi government requested it.
There are currently about 160,000 foreign troops in Iraq, including 138,000 Americans who have borne the brunt of attacks against coalition forces.
A number of coalition members, however, have expressed growing concern over the lengthening mission, while Washington has warned against too hasty a pullout.
"Madrassas around the world continue to turn out new recruits from the ranks of the misguided and the misled"
US Defence Secretary
Meanwhile, US Defence Secretary Donald Rumsfeld said the US cannot win the "war on terrorism" by military means alone or without the support of other countries.
"Despite the successes, new terrorist leaders continue to step forward, and new networks emerge," he said in a speech prepared for delivery before a foreign affairs group in Philadelphia, Pennsylvania.
"Madrassas around the world continue to turn out new recruits from the ranks of the misguided and the misled," he said.
To win, the US must find ways to reduce the ideological appeal of violent extremism.