Radical Iraqi Shiite cleric Moqtada Sadr vowed to fight on until his "last drop of blood" as intense clashes engulfed Najaf for a fifth day, while six people were killed in a suicide bombing Monday.
"I will defend Najaf until my last drop of blood," Sadr told a news conference in Imam Ali shrine, as mortar and machine-gun fire rocked this Shiite holy city in central Iraq.
"Do not call them fighters of the Mehdi Army any longer, call them defenders of the city," he said.
"The occupiers must go, and then the democratic process can start" in Iraq, said Sadr, a day after Prime Minister Iyad Allawi visited Najaf to call on the cleric's Medhi Army to withdraw.
Artillery and tank fire, backed by air power, battered central Najaf where Shiite Muslim militiamen were hunkered down in the vast cemetery and near the shrine, a Mehdi stronghold since Sadr's spring uprising against foreign troops.
Two dead Mehdi Army fighters were sprawled in the square outside the mosque.
Since the fighting erupted Thursday, when the Mehdi Army attacked the main police station and governor Adnan al-Zorfi requested US support, the military estimates that 300 insurgents have been killed.
But a spokesman for Sadr has insisted that only 15 militiamen have been killed and 35 wounded, the majority from cluster bombs fired by US troops.
In Sadr's Baghdad stronghold, mortar bombs were fired at the district council hall in the sprawling Shiite slum of Sadr City from around 8:00 (0400 GMT).
Missing the council hall, they slammed into neighbouring houses, but there were no reports of casualties.
Abu Moqtada, a local Mehdi Army leader, said the militia had fired 10 to 15 mortars at the building. "As long as we continue to fight with the government, incidents like this will happen," he said.
Militiamen prowled the streets armed with Kalashnikov assault rifles and rocket-propelled grenades (RPGs), and an AFP correspondent saw four US tanks outside the district hall.
Elsewhere, a suicide bomber blew up a car in Baladruz, near the restive city of Baquba, northeast of Baghdad, killing six Iraqis and wounding 16, including an official in the local provincial government, police said.
The bomb exploded as Akeel Hamid, an assistant to the governor, left his home in Baladruz, said Lieutenant Mohammed Abed.
In western Iraq, the military reported that a US marine was killed in the volatile province of Al-Anbar while conducting what the military described as "security and stability operations".
More than 685 US troops have been killed in action in Iraq since the start of the 2003 US-led invasion, based on Pentagon statistics.
Sixteen Iraqis were killed and 87 wounded in attacks in the past 24 hours, according to Iraq's health ministry. No statistics were available from Najaf, however.
In southern Iraq, a spokeswoman said a British base came under mortar fire twice overnight and that several British patrols were targeted with small arms and RPGs in the restive city of Amara.
Meanwhile, Iran's mission in Baghdad said it had no news about a staff member "detained" by an Islamic group "for stirring sectarian strife and for activities outside his diplomatic duties", said a statement on Arab television.
Al-Arabiya showed pictures of Fereydun Jahani's passport, identity and business cards along with what appeared to be footage of him speaking, without sound, against a black backdrop.
The television also flashed identity cards from the Iranian Revolutionary Guards, casting doubt on claims that Jahani was only a diplomat.
He disappeared on Wednesday as he travelled to the central city of Karbala to open an Iranian consulate under an agreement with Iraq's interim government, the embassy said.
Bahrain clamps down on Shiite activists