"The latest numbers have gone up. We have an estimated 109 fatalities," said spokesman for the 1st Infantry Division, referring to Iraqi insurgents.

The attack amounted to the first major effort by US and Iraqi forces to reclaim a rebel enclave in the Sunni Muslim triangle ahead of nationwide parliamentary elections scheduled for January.

"In response to repeated and unprovoked attacks by anti-Iraqi forces, Iraqi Security Forces and Multi-National Forces secured the government and police buildings in Samarra early in the morning of October 1 in support of the Iraq Interim Government and the people of Samarra," the military said.

The offensive came a day after a string of bombings across the country that killed at least 49 people, including 32 children in a series of blasts as US troops handed out candy at a government-sponsored celebration to inaugurate a sewage plant in Baghdad.

The bloodiest attack in Iraq was a twin car bombing at the site of a ribbon-cutting ceremony for a new water pumping station in the poor Al-Amel neighbourhood of southwest Baghdad.

A crowd of curious children had gathered to watch the ceremony when the bombs went off, sending clouds of black smoke billowing into the air.

A bloodied witness said he helped carry out 32 bodies of children from the rubble.

US troops and one battalion each from the Iraqi army and national guard stormed the city before dawn on Friday after a previous arrangement signed on September 9th for US forces to enter the town and patrol peacefully fell apart one week ago.

An AFP correspondent in the city said many homes were destroyed in the city's Al-Jubairiya and Al-Qadisiyah neighbourhoods as the city's streets were completely deserted.

The violence flared Thursday night when US soldiers spotted three speed boats unloading explosives at 6:00 pm (1500 GMT) on the bank of the Tigris river, said Master Sergeant Rober Powell from Tikrit.

A gunfight ensued and several insurgents were killed, Powell said.

Insurgents in a boat then fired off mortars into the city and US forces opened fire, killing four of them at 7:09 pm (1609 GMT), he added.

Loud explosions started to shake the town at 9:00 pm (1800 GMT), Samarra residents said.

Within hours, US troops marched into the heart of the city, with armored vehicles rumbling down the street and AC-130 helicopter gunships roaring overhead.

Sporadic clashes erupted through the early morning, Powell said.

The governor of Salahuddin province, where Samarra is located, had warned on Thursday that new fighting risked plunging surrounding towns and cities into violence.