The U.S. military spokesman, meanwhile, said the capital's spiraling murder rate had eased since the end of the Muslim holy month of Ramadan early this week — possibly because of the massive deployment of U.S. troops searching for a missing soldier.
Police in Baqouba said at least 42 people were injured in the fighting there, while in Najaf, south of Baghdad, authorities temporarily closed Iraq's holiest Shiite shrine after receiving a tip that suicide bombers wearing explosives belts had infiltrated city.
The military released news of five new American deaths, those of a Navy sailor and four Marines, all of whom died in fighting Wednesday in the volatile Anbar province, west of Baghdad and a hotbed of the Sunni resistance to U.S. forces and their Iraqi government allies.
At least 96 U.S. troops have died so far this month, equaling the level for the whole of October 2005 — a factor in rising anti-war sentiment in the United States that has prompted calls for President Bush to change strategy.
, but he does not want the United States to pull out the troops or set timetables for withdrawal.
In related developments:
"We did in fact see a tremendous downturn in the number within our clear areas which we are trying to watch very closely," Caldwell said at a weekly news briefing. "It could be a multitude of things that are bringing down the level of violence."
The fighting around Baqouba, 35 miles from the capital, marks the latest outbreak of bloodshed involving militants believed to be members of the Mahdi army militia loyal to hardline anti-American cleric Muqtada al-Sadr.
Ghassan al-Bawi, police chief of surrounding Diyala province, said those killed included 12 police officers and 18 gunmen.
The clashes followed fighting earlier this week between the Mahdi army and police aligned with a rival Shiite militia, the Badr Brigade, in the southern city of Amarah. At least 31 people were killed, including six police officers who were dragged out of their houses.
Mahdi militiamen have recently moved aggressively into several mixed areas around Baghdad, killing some Sunnis and forcing many others to flee their homes in a form of sectarian cleansing. Militia killings last week in Balad, near Baqouba, forced U.S. troops to return to the area after Iraqi security forces were unable to stem the bloodshed.
In the northern city of Mosul, authorities extended an overnight curfew until 3 p.m. local time on Friday after Sunni gunmen distributed leaflets proclaiming the mixed Sunni-Kurdish area a part of an Islamic state declared earlier this month by an insurgent umbrella group, the Mujahedeen Shura Council.
No insurgent group holds enough power to enforce such a decree, and the announcement of the Islamic state's formation has been viewed primarily as a propaganda ploy aimed at diminishing the U.S.-backed national government.
Arab Sunni insurgents and members of the Kurdish minority have been fighting for the upper hand in Mosul and a recent wave of attacks have killed dozens of civilians. On Thursday, five bullet-riddled bodies, including those of two plainclothes policemen, were found dumped around the city, a spokesman for the Ninevah provincial police said.
October has been especially deadly for Iraqi security forces and civilians, with about 1,000 Iraqis killed in war-related violence this month, including about 300 police and soldiers.
Caldwell said the search for the missing soldier, an Iraqi-born linguist abducted while visiting relatives on Monday, had resulted in a more check points and troops on the street, something that may have contained violence.
U.S. troops have blocked parts of the capital and searched door-to-door and by air with helicopters and drones. The soldier's name has been withheld to protect his family still in Iraq, Caldwell said.
The U.S. military reported Iraqi forces in Hillah south of the capital detained 11 suspected members of a murder and kidnapping cell that had targeted Iraqi and U.S. troops with mortars and roadside bombs. Another Iraqi unit killed a member of similar group in a gunfight during raid in Khalis, the military said.
U.S. commanders have been pushing Iraqi forces to take a leading role in the fight against insurgents, militias and death squads, one of a series of political and security goals Iraqi leaders have targeted in coming months.
In a snapshot of operations against Sunni insurgents, Caldwell said an offensive in the area around Shakariah, southwest of Baghdad — described as a "known terrorist sanctuary" — resulted in Iraqi and U.S. forces uncovering 130 weapons caches containing enough explosives to produce 1,000 roadside bombs.
The forces also drove insurgents from a half-built power plant in the Yusufiyah region that had been used as a staging base for attacks and a site where captives had been held in cages and tortured, he said.