Five US soldiers were killed in northern Iraq on Sunday while an advisor to Iraq's council of ministers was gunned down in Baghdad last morning, an interior ministry official said.

Insurgents also kept up pressure on the US military. Three American soldiers were killed in two separate attacks in the northern city of Mosul on Sunday, the military said, and another US soldier was killed by a bomb blast near Tikrit.

Officials on Monday said three Task Force Freedom soldiers were killed in Mosul, 360km northwest of Baghdad. Details were not released.

A fourth Task Force Liberty soldier died of wounds sustained in 10 a.m. car bomb attack against his combat patrol just north of Tikrit, 135km north of Baghdad, the military said in a statement.

A fifth soldier was fatally injured in a vehicle accident at 2:30 p.m. near Kirkuk, 235km north of Baghdad, officials said. The cause of the accident was under investigation.

The names of the five soldiers were being withheld pending next-of-kin notification.

Police said a car bomb blew up outside a restaurant in northern Baghdad at lunch time, killing at least four people and wounding more than 100.

The truck bomb exploded near the mayor's office in the town of Tuz Khurmatu, south of the oil city of Kirkuk, killing five and wounding 18.

Insurgents also struck in Samarra, targeting a US base with two car bombs and a suicide bomber strapped with explosives, killing four Iraqis and wounding four US soldiers.

Earlier, gunmen in Baghdad shot and killed Wael Rubaie, an official in the operations room of the Ministry of State for National Security, a government statement said yesterday. His driver was also killed.

al-Qaeda's wing in Iraq, led by Jordanian militant Abu Musab al-Zarqawi, said it was behind the assassination.

The bloodshed came as mostly Sunni Muslim insurgents stepped up a campaign of attacks that have killed more than 500 people in the three weeks since a new Shia-led government came to power with the promise of stability.

The wave of suicide bombings, assassinations and ambushes have raised fear that violence could spark civil war.

Among the dead in Tuz Khurmatu was the brother of a senior official in one of Iraq's main Kurdish parties, the Patriotic Union of Kurdistan, police said.

The official, Mohammed Mahmoud Jigareti, was wounded in the blast. Both men had been in a car that was entering the mayor's office compound when the bomber struck.

Insurgents also have been targeting the US military.

Three American soldiers were killed in separate attacks in the northern city of Mosul on Sunday, the military said, and another US soldier was killed by a bomb blast near Tikrit.

More than a dozen senior Iraqi government officials have been killed in Baghdad in well planned attacks in recent weeks.

US and Iraqi forces detained 285 suspected insurgents in the western Baghdad district of Abu Ghraib after a widespread search, the US military said. It said the operation called "Squeeze Play" was designed to kill or capture guerrillas who have been staging attacks in the capital.

Iraqi officials are hoping to give Sunnis a bigger role in politics after they were sidelined in Jan. 30 elections, in a strategy designed to defuse the Sunni-led insurgency.

Tit-for-tat killings between Shiaa and Sunnis have raised fears that violence will push Iraq toward civil war. A senior US official said he didn't think such an outcome was likely, but added it was on his "list of things to worry about."

Leaders of Iraq's two Muslim sects have moved rapidly in the past few days to try to dispel the rising sectarian tensions.

Moqtada al-Sadr, a young cleric who led two armed uprisings against US troops last year, on Sunday sent a delegation to see the Sunni Muslim Clerics' Association, and another team met representatives of SCIRI, the main Shias party, and its militia, the Badr Organisation. Officials in Sadr's office said a summit between the two sides may be held. (Reuters, AP)