Coalition forces are engaged in a fifth day of battles with Sunni insurgents and rebellious Shi'ites in several parts of Iraq.
Some of the worst clashes are reported in the mainly Sunni town of Fallujah, where four American civilian contractors were killed and their bodies mutilated by a mob last Wednesday.
U.S. Marines have vowed to "pacify" the town, which has been a constant source of attacks on coalition forces.
Thousands of Iraqis made their way to the besieged town Thursday, bringing food and medical supplies to the residents.
Local hospital officials report dozens of Iraqis killed and wounded in the fighting, but there has been no independent confirmation of the casualty figures.
In the southern holy city of Karbala, Polish and Bulgarian forces are fighting members of the Shi'ite Al-Mahdi militia. Reports say the clashes erupted late Wednesday and continued through the night.
Supporters of the militia's radical leader, cleric Moqtada al-Sadr, began fighting with coalition troops earlier this week, after the United States shut down the newspaper belonging to the cleric.
The situation in Karbala could be complicated by the tens of thousands of Shi'ite pilgrims who have begun converging on the holy city to mark a major Shi'ite religious occasion (Arbaeen) that has its climax this week.
A senior commander in Iraq, General Ricardo Sanchez, say the Shi'ite militia has at least partial control of the cities of Kut and Najaf, and that the coalition is working to re-take them.
At least 35 coalition troops have also been killed in clashes this week across the country.
In a separate development, the U.S. appointed Iraqi interior minister, who is a Shi'ite, says he has resigned at the request of the U.S. administrator.
On Wednesday, Iraq's most influential Shi'ite leader, Grand Ayatollah Ali al-Sistani called for calm, on all sides. In a statement issued late Wednesday, the Grand Ayatollah also condemned the way U.S. led forces have been handing the escalating situation.
Despite the current violence, President Bush has insisted that plans to turn over sovereignty to an Iraqi interim government on June 30th will go ahead.