Three US Marines have been killed in renewed clashes in the Iraqi city of Fallujah.
The fighting erupted as residents began returning for the first time since the US offensive started six weeks ago.
The government had authorised a group of 2,000 to return to inspect their homes but only about 500 arrived. More than 250,000 people fled the offensive which left the city in ruins.
Meanwhile, US Defence Secretary Donald Rumsfeld said it would be a mistake to think that violence in Iraq would subside after next month's scheduled elections.
He was speaking at a Pentagon news conference at which it was disclosed that the US military believes a suicide bomb attack was behind the deaths of 22 people, including 18 Americans, at a base in Mosul this week.
Mr Rumsfeld said the insurgents were determined not to give in to the post-Saddam administration, and that coalition and Iraqi government forces had to do everything possible to see that the militants failed.
Mr Rumsfeld rejected suggestions that not enough was being done to protect the lives of US troops.
