The fresh violence came after 30 people were killed when a Baghdad house rigged with explosives blew up during a police raid.

Despite the volatile security situation, US President George W. Bush insisted Iraq's landmark national elections must go ahead, while a hardline Islamist militant group reiterated its intention to cause bloodshed on polling day January 30.

In the northern city of Mosul, insurgents detonated car bombs against a US patrol and a combat outpost and about 50 fighters launched an assault on the outpost, firing small arms, rocket-propelled grenades and mortars, the military said.

US forces called in air strikes and at least 25 insurgents were killed, said Lieutenant Colonel Paul Hastings.

A military statement Thursday said a US soldier died of wounds suffered in one of the car bombings.

Masked gunmen were seen running down Mosul's deserted streets, firing off guns and rocket-propelled grenades, as a column of smoke shot up into the sky, an AFP correspondent reported.

Violence has paralysed the city of 1.5 million people, where US forces are expected to increase their numbers ahead of the elections for an Iraqi national parliament.

As the clock ticked down to the election, doubts loom over whether US and Iraqi forces can pacify cities like Mosul, a bastion of the Sunni Muslim minority whose alienation from the US-backed political order is fueling the lethal insurgency.

The Iraqi government said it had captured in Mosul a militant linked to al-Qaeda operative Abu Musab al-Zarqawi, who has a 25-million-dollar price on his head.

The government identified the fighter as 33-year-old Abu Marwan, a senior commander with Mosul-based Abu Talha groups, which the government said was linked to the Jordanian-born Zarqawi.

The deaths raised to almost 100 the number of people killed in Iraq in 48 hours as insurgents carried out a series of brazen attacks Tuesday on police stations and checkpoints in the Sunni Muslim heartland north of Baghdad.

Apparently lured into a trap, police raided a home in Baghdad's squalid western Ghazaliya district late Tuesday, and were still inside when a massive blast leveled the house, an interior ministry official said.

Thirty people died, six of them police, the ministry said. Another 25 were wounded, including four policemen, and four police were listed as missing.

The attack resembled those in Fallujah during last month's US-led offensive on the city, where rebels rigged homes to blow up on ground troops.

The US army estimated that up to 900 kilograms of explosives were used in the blast.

"What kind of Muslim stores these kinds of explosives in the middle of innocent civilians," neighbour Omar Hussein demanded in rage.

Kidnappings of foreigners for money or political motives appeared to be back after a relative lull during the assault on Fallujah in November.

Two Lebanese businessmen were kidnapped by masked gunmen from their home in Baghdad's upscale Mansur neighbourhood, scene of previous abductions, said police Thursday.

About 30 Lebanese working for private companies in Iraq have been kidnapped and later freed. However, in September, one was killed by his captors and three others killed during an attempted kidnap.

In other unrest, an Iraqi businessman, a female engineer working for the US military and a Turkish truck driver were killed in separate attacks to the north of Baghdad, police said.

And Iraqi authorities said they had arrested 59 people, including an Egyptian, suspected of involvement in violence after raids by the Iraqi National Guard in Baghdad and its regions.

Bush on Wednesday was adamant that Iraq's election must take place on time.

"It's very important that these elections proceed," Bush told reporters near his ranch in Crawford, Texas.

US and Iraqi officials have warned that insurgents will only escalate their violence in the build-up to Iraq's first free elections since the 1950s that Washington wants to serve as a democratic model for the Middle East.

An al-Qaeda linked group, Ansar al-Sunna, which claimed responsibility for last week's deadly attack against US troops in Mosul, renewed a threat to attack polling stations during the election, in a statement posted on its website.

Meanwhile, it emerged that former US attorney general and left-wing activist Ramsey Clark is to join the defence team of Saddam, who is in US custody awaiting trial on charges of crimes against humanity.