FALLUJAH, Nov 9: US tanks rolled into the centre of Fallujah on Tuesday in the largest military onslaught since last year's war, seizing one third of the rubble-strewn Iraqi city in fighting with rebels that left several troops dead.

"Tanks are patrolling parts of Michigan", the military road cutting through the centre of Fallujah, said marine Colonel Michael Schupp, the commander leading the marines into battle.

Clashes in the city, considered the main stronghold of the insurgency in Iraq, had died down by Tuesday evening, a correspondent in Fallujah said, barely 24 hours after the massive US-Iraqi operation was launched to retake the city from rebels.

Underlining the chronic instability prevailing in Iraq's heartland, Prime Minister Iyad Allawi's office also announced that a nighttime curfew would take effect in Baghdad.

In Fallujah, only occasional tracer fire and the sound of crying babies and hysterical laughter played eerily by US psychological operations forces could be heard.

"The military controls one third of the city," a marine officer said earlier in the day.

An exact casualty toll was unavailable from the city, where estimates for the number of its 300,000-strong population who fled ahead of the assault vary widely from 20 to 90 per cent.

US CASUALTIES: US Lieutenant General Thomas Metz said "about a dozen" US troops had been killed so far in the offensive, without giving a precise toll. "I would not want to characterize it beyond that. It is light," he said.

The marines said more than 20 Iraqis were killed in a day of fighting, half of them by sniper fire, in their section of the enclave in the northwest.

Some bodies were buried under buildings that had been floored by artillery and ground bombardments, a reporter said.

"As for casualties on the insurgents' side I can tell you that they are dying. A lot of them are dying and this is a good thing," marine spokesman Lieutenant Lyle Gilbert said.

In a two-pronged assault on Fallujah that began late on Monday, thousands of US troops, followed by crack Iraqi soldiers, poured into the northwestern Jolan neighbourhood and the Askari district in the northeast.

Rebel fighters, their faces covered in scarves, were firing gunshots from run-down houses at US soldiers before rushing on to escape a punishing barrage of American artillery and missiles, an AFP correspondent said. Sunni and Shia figures have condemned the assault, dubbed Operation Dawn, with Iraq's main Sunni party quitting the government in protest.

"The residents of Ramadi condemn the attack against Fallujah and we appeal to the inhabitants of Ramadi to wage jihad against the American occupants who want to eradicate Islam," said one man.

Ramadi was the scene of clashes between US forces and insurgents during the last 24 hours. At least seven Iraqis were killed, medical sources said.

Mosul was also the scene of unrest, with two US military personnel killed when their base in the northern Iraqi city came under mortar fire.

BAQUBA: Insurgents attacked three police stations in and near the town of Baquba on Tuesday, officials said, but there were conflicting casualty reports.

The official in charge of Baquba's main morgue, Ahmed Fuad, told Reuters 45 bodies were received following the string of coordinated attacks, adding that 32 people had been wounded.

Police initially reported that insurgents firing rocket-propelled grenades and assault rifles had killed 25 people in the attacks on the Wahda, Tahrir and Mafraq police stations around Baquba.-Agencies