US-led coalition soldiers across Iraq are reported to be engaged in fresh clashes with Sunni and Shia militants.
Falluja is still ringed off with US troops
A US military convoy was attacked west of Baghdad on Thursday - hours after US troops fought street battles with both groups in parts of the Iraqi capital.
Bodies were said to be in the streets of Falluja, where about 300 people have been killed, hospital officials say.
In another development, Iraq's interior minister has resigned at the request of senior US administrator Paul Bremer.
Nuri Badran, a Shia, said Mr Bremer wanted to redress an imbalance between Shias and Sunnis within the Iraqi Governing Council after the appointment of a defence minister - also a Shia.
But he added: "Bremer is not satisfied with the performance of the interior ministry."
The top US military commander said coalition operations would continue across Iraq until the insurgents were defeated.
General Ricardo Sanchez said the militia loyal to radical Shia cleric Moqtada Sadr - which started the current violence over the weekend - would be pursued in a "robust" manner until their leader was no longer a threat.
The clashes this week are being seen as the heaviest since Baghdad fell to US-led forces a year ago.
At least 30 coalition soldiers have been killed.
Sunni and Shia Muslims got together to march to Falluja
In other developments:
- Arabic TV channel al-Jazeera shows pictures of three Japanese nationals reportedly taken hostage by an unknown Iraqi group, which has threatened to kill them unless Japan pulls its forces out of the country
- US helicopters destroy the Baghdad offices of Moqtada Sadr.
- A convoy of Iraqis set off from Baghdad to take humanitarian aid to the besieged city of Falluja.
- General Sanchez says the US-led coalition will "imminently" regain control of the holy city of Kut, currently in the hands of militiamen loyal to Mr Sadr
- Japanese troops in the southern town of Samawa are apparently targeted by a number of explosions. There are no reports of injuries.
On Thursday, a US convoy came under attack on the western outskirts of Baghdad - and several vehicles could be seen in flames.
The US military has not confirmed the incident, which came hours after US troops fought intense street battles in the capital.
The heaviest of the fighting has been reported in Falluja.
A correspondent for French news agency AFP, told the BBC there was a constant rumble of explosions throughout the city - some caused by mortars and rockets fired by the insurgents.
Between 280 to 300 Iraqis have been killed and at least 400 wounded in fighting this week, the director of the main hospital, Rafi Hayat, said on Thursday.
Iraqi witnesses say about 45 people died during a US air strike on a mosque compound on Wednesday. The US said only one had died.
But the scenes of intense fighting there over recent days have increased tensions in the rest of Iraq, says the BBC's Richard Lister.
Baghdad residents have been lining up to give blood and donate food and water to residents of Falluja.
General Sanchez, for his part, insisted the people of Falluja would have to decide between supporting the insurgents or his troops.
US Defence Secretary Donald Rumsfeld had said some "seasoned" US troops in Iraq might be kept there longer than planned to deal with the growing violence.