FALLUJAH, April 29: United States Marines eased their grip on Fallujah on Thursday, but details of a deal with former Iraqi army officials remained sketchy and new airstrikes on the besieged city showed a month-old uprising was not over.

Within hours of Marine officials and Fallujah's police chief saying troops were pulling back from some siege positions around the town, 50kms west of Baghdad, US warplanes again pounded districts where as many as 2,000 guerillas are holed up.

As darkness fell, gunfire crackled across streets where ambulances raced to the scene of the bombings. Doctors say about 600 people have been killed since Marines encircled the city at the beginning of this month after the killing of four American security guards, whose bodies were then mutilated in public.

Fallujah's police chief said the US withdrawal would be completed by Friday. US officials seemed to have backed away from insistence on conducting joint patrols with Iraqi forces inside the city, he said.

A Marine spokesman in Fallujah confirmed US forces were pulling back from some areas under a deal agreed with former senior officials of Saddam Hussein's old Iraqi army. It was unclear who the men were or what influence they had over the guerillas, some of whom, US officials say, are foreigners.

In Washington, US Deputy Defence Secretary Paul Wolfowitz said the situation in Fallujah was "confusing" but a deal was being worked on. "The goal has got to be to try to isolate the killers from the population so that if military action is necessary it can be done with a minimum of civilian casualties," said Mr Wolfowitz.

Previous deals in the town, notably a ceasefire two weeks ago, have broken down and US airstrikes this week and tough talk by President George Bush seemed to herald a possible all-out assault. The Pentagon said it had sent more tanks to Fallujah and other restive areas around Baghdad.

Thousands of civilians have left the town since the siege, a focus for increasing Iraqi dismay with the occupation, especially in towns around Baghdad. In Baghdad, four civilians died when Marines opened fire on a minibus at a checkpoint, setting the vehicle ablaze. Such incidents have angered many Iraqis who had welcomed the fall of Saddam Hussein.

NAJAF: Around Najaf, US forces set up roadblocks, tightening a squeeze on the Mehdi Army militia loyal to Shia leader Moqtada al Sadr, who has taken refuge in the holy city.