US-LED forces battled Sunni guerrillas and grappled with an uprising by Shi?ite militiamen yesterday in a war on two fronts that has killed more than 30 soldiers and 160 Iraqis in three days.

A US defence official said up to 12 Marines had been killed on Tuesday in an attack at the governor?s palace in Ramadi in central Iraq?s Sunni heartlands west of Baghdad.

It was one of the costliest battles for US forces in Iraq since the war that toppled Saddam Hussein began a year ago, and brought to around 30 the number of US soldiers killed in action since Sunday. A Ukrainian and a Salvadoran soldier have also been killed in clashes with Shi?ite fighters.

The White House said the losses would not weaken its determination. ?Our resolve is firm, our resolve is unshakeable and we will prevail,? White House spokesman Scott McClellan said.

In Falluja, where Marines were pursuing a major crackdown after last week?s killings of four American private security guards, doctors said 36 people had been killed on Tuesday. Among the dead were 25 civilians in a house destroyed by what locals said was a US helicopter strike. A US military spokeswoman in Baghdad said she had no word on the incident.

Intense fighting raged in Falluja yesterday. Heavy gunfire and blasts could be heard during a live report from the city by a correspondent for the Arabic news channel Al Jazeera.

The US defence official also said ?a significant number? of Iraqis had died in the Ramadi battle. US Marines in Falluja and Ramadi launched ?Operation Vigilant Resolve? this week to hunt down those involved in the killing of the four US guards.

After they were killed, a crowd of Iraqis set the bodies ablaze, mutilated them and hanged two of them from a bridge.

Locals in Falluja said a US helicopter had gone down on Tuesday but the US military said it had no information.

New Vietnam?

Elsewhere in Iraq, followers of Shi?ite cleric Moqtada al-Sadr fought gun battles with foreign troops in the southern cities of Nassiriya, Amara and Kut on Tuesday and vowed to pursue a revolt that has claimed over 130 lives since Sunday.

Police and hospital officials said five Iranians and three Iraqis had ben killed on Tuesday evening when foreign troops opened fire on their vehicle after it ran a checkpoint near Kerbala.

The uprising by Shi?ites raised fears in Washington that US forces, already battling Sunni insurgency, faced a Vietnam-style quagmire.

The clashes with Shi?ites are a new front for US-led forces trying to pacify Iraq ahead of a June 30 handover of sovereignty to an Iraqi government.

Sadr appealed to all Iraqis, whatever their religion, to help expel the occupiers. ?This insurrection shows that the Iraqi people are not satisfied with the occupation and they will not accept oppression,? he said in a statement.

Iraqi Foreign Minister Hoshiyar Zebari, in London for talks with British Prime Minister Tony Blair, said thousands more foreign troops might be needed to maintain order.

US Defense Secretary Donald Rumsfeld said if commanders on the ground asked for more troops they would be sent.

President George W. Bush vowed the campaign by Sadr?s supporters would not derail Washington?s plans. ?We will pass sovereignty on June 30,? he told a campaign rally in Arkansas. ?We?re not going to be intimidated by thugs and assassins.?

A US opinion poll showed support for Bush?s handling of Iraq at a new low of 40 percent, with 44 percent wanting US troops withdrawn.

US Democratic Senator Edward Kennedy, a key backer of John Kerry?s bid to unseat Bush in November?s presidential election, said Iraq had become ?George Bush?s Vietnam? ? a comparison rejected by Iraq?s US governor Paul Bremer.

Since the US-led invasion, 429 US soldiers have been killed in action in Iraq, excluding Tuesday?s deaths in Ramadi.

Alistair Lyon