Two soldiers were killed in a drive-by shooting attack on their convoy in central Baghdad on Thursday, while another was killed a day earlier in an "indirect fire attack" -- a term normally designating mortar fire -- on a base in the western flashpoint city of Ramadi, west of Baghdad.

Another soldier died in a road crash after a bomb exploded near US patrol vehicles overnight Thursday to Friday near Taji, north of the capital.

The total number of US service personnel who have died in Iraq since the March 2003 invasion now stands at 1,623, according to an AFP tally based on Pentagon figures.

On Thursday gunmen killed an Oil Ministry official and escalating violence claimed at least 24 more lives, fuelling fears Iraq may be moving toward civil war.

The oil official, Ali Hameed, was shot outside his home, police said. Insurgents have assassinated dozens of government officials in Baghdad over the past two years.

Mainly Sunni Muslim insurgents have stepped up attacks on officials and security forces since a Shia-led government was announced last month. They have killed more than 500 people in a campaign that has challenged government promises of stability.

In the worst violence on Thursday, eight people were killed in the northern city of Mosul after insurgents attacked the house of a local Sunni Muslim politician, witnesses and hospital officials said.

The politician, Fawwaz al-Jarba, said his driver and three guards were among the dead. He said US troops responded to his request for help. Witnesses said the deaths were caused by clashes between US troops and the insurgents.

Jarba is distrusted by some Sunni Arabs because he won election to parliament as a member of a Shia-dominated coalition.

In Baghdad, a car bomb near a Shia Muslim mosque killed at least two people and wounded five, police said.

A university professor was shot dead, an Iraqi soldier was killed in a suicide bombing, and four others were kidnapped.

Gunmen opened fire on a US convoy, and two soldiers later died from wounds suffered in the attack, the military said. A roadside bomb also killed an American soldier in the capital, the military said.

The escalation in violence has raised concerns the country could erupt into a full-scale civil war. Discoveries of people killed execution-style have stirred sectarian passions.

More than 50 bodies have been found since Saturday. Most victims were Shia Muslims but some were Sunnis.

Four more bodies were found on Thursday, near Saddam Hussein's home town of Tikrit. Police said they had been shot.

Top Sunni cleric Harith al-Dhari this week publicly accused the Badr Brigades, the militia of the main Shia political party, of assassinating Sunni preachers, in a sign of worsening sectarian tensions.

It was the first time Dhari had publicly accused the armed wing of the Supreme Council of the Islamic Revolution in Iraq (SCIRI), which was part of the Shia coalition that won a majority in parliament in Jan. 30 elections.

Dhari's Muslim Clerics Association called for a three-day closure of Sunni mosques in protest at the killings and said Sunnis would not keep silent.

The top Badr Brigades official has denied the accusations and said Sunnis and Shias should avoid sectarian strife.

Shia Arabs and Kurds, who dominate Iraq's parliament, have promised to give Sunni Arabs a key role in politics, even though the minority won only 17 of parliament's 275 seats.

Sunni Arabs were the most powerful group in Iraq during Saddam's rule, but largely stayed away from the elections and make up the backbone of the insurgency.

So far, most Shias have heeded calls by moderate clerics to show restraint. But the recent explosion of violence has strained their patience.

In Mosul, hospital officials said two people were killed when a bomb exploded prematurely in their car during a suicide mission.

Police said a roadside bomb killed two policemen in Baquba, and a police officer and his father were shot dead in Samarra. In the province of Anbar, gunmen killed a local police chief.

In Iskandariya, just south of Baghdad, another roadside bomb killed a policeman and wounded three, police said.