BAGHDAD, Jan 27: At least 30 people were killed in Iraq on Thursday as guerillas intensified attacks on Iraqi and US targets, and election workers backed by troops started distributing ballot boxes for Sunday's vote.

Militants have promised an all out onslaught against the election, but US President George Bush urged Iraqis to brave death threats and seize what he termed a "historic opportunity" to vote.

New attacks across the country followed the deaths of 31 US military personnel in a helicopter crash in western Iraq on Wednesday, while six other US soldiers died elsewhere in the deadliest day for American forces since the March 2003 invasion.

In the deadliest attack, a car driven by a suicide bomber rammed an Iraqi army patrol in Samarra, a mainly Sunni Arab city north of Baghdad where US and Iraqi forces launched a massive operation last October to wrest control from guerillas before the vote.

As security forces sealed off the sector to evacuate victims, a second car burst onto the scene from the direction of a nearby hospital. Eight soldiers and three civilians were killed, police said.

In Baquba, north of the capital, a car bomb attack on a provincial government headquarters killed five people. "A peace conference gathering former Baathists, tribal leaders, clerics and political officials, was being held in the building at the time of the attack," said police lieutenant colonel Mohammed Mahmud.

South of Baghdad, in the so-called triangle of death, a home made bomb killed five Iraqis and wounded 15 on the road between Mahmudiyah and Latifiyah. A US marine was killed in the same area.

Another six people were killed in clashes between Iraqi and US troops and guerillas in Samarra and in Ramadi, an insurgent stronghold west of the capital. New bomb attacks rocked the northern oil centre of Kirkuk, one targeting a US military convoy.

A police officer was killed in Saddam Hussein's hometown of Tikrit on Wednesday night. Another US soldier was shot dead overnight in Diyala province, north of Baghdad.

With some 40 polling stations already destroyed, even the distribution of ballot boxes for Iraq's estimated 14.2 million eligible voters underscored the tension hanging over the poll.

Militants loyal to Iraq's most wanted man, Al Qaeda front man Abu Musab al-Zarqawi, issued a dire warning to would-be voters on Wednesday. In the Shia holy city of Najaf south of the capital, police, US and Iraqi forces sealed off a one kilometre perimeter around a school being used as a polling station as boxes were taken in.

Despite the security efforts by the Iraqi government, backed by more than 150,000 US and other foreign troops, fears of greater violence hit world oil prices. New York's benchmark contract - light sweet crude for delivery in March - climbed 11 cents to 48.89 dollars a barrel.

In London, the price of Brent North Sea crude for March delivery gained 15 cents to 46.66 dollars a barrel. Sunday's election has been marred not only by growing violence but also by a boycott by many Sunni politicians concerned that the election will cede power to the long-oppressed Shia majority.

Mr Bush said he was heartened by comments made by Shia leaders who had promised that the new government would be inclusive and allow members of the Sunni community to take part in deciding Iraq's future. -AFP