US troops killed in ambush

Two American soldiers have been killed and two others wounded in an explosion in the northern Iraqi city of Mosul.

A crude bomb or landmine exploded by the side of a road as a US military convoy was passing.

The BBC's Jill McGivering, in the capital Baghdad, says attacks on American forces occupying Iraq are now averaging about 25 a day.

Saturday morning's attack comes exactly six months after US President George W Bush declared major hostilities over.

The soldiers who were killed and injured were from the 101st Airborne Division.

"There was a huge blast. The two drivers of the vehicles were definitely killed," policeman Abdul-Rahman Fawaz, who witnessed the explosion, told Reuters news agency.

'Day of resistance'

In Baghdad, there have been widespread rumours that militants are planning attacks this weekend.

POST-WAR: KEY EVENTS 1 May: Bush declares 'major combat' over 13 July: Iraqi Governing Council appointed 22 July: Saddam Hussein's sons Uday and Qusay killed 19 August: UN special representative Sergio Vieira de Mello among 20 killed in attack on UN HQ in Baghdad 29 August: leading Shia Muslim politician Ayatollah Mohammed Baqr al-Hakim among 80 killed in bombing in Najaf 27 October: Dozens killed in Baghdad bombings, including attack on Red Cross HQ 1 November: 122 US soldiers killed since 1 May (114 killed during war) Source of attacks unclear US weighs options

Leaflets have been circulating threatening a day of resistance against the US occupation, and the US and Australian diplomatic missions have issued security warnings to their nationals.

Our correspondent says some Iraqi residents kept their children away from school on Saturday.

The past week has seen a surge in attacks across Iraq, including a series of bombings in Baghdad on Monday that left 36 people dead, making it the bloodiest day in the capital since the start of the US-led occupation.

Faced with continuing attacks, US forces have stepped up their efforts to track down suspected former regime loyalists who they blame for much of the violence.

American troops have erected barbed wire around Saddam Hussein's home village near the northern town of Tikrit.

Soldiers have set up checkpoints in and out of the village of Uja, where residents have been ordered to register for identity cards.

Meanwhile, US Secretary of State Colin Powell has said there is no evidence that Iraq's deposed leader, Saddam Hussein, is behind the ongoing wave of attacks in the country.

In a US television interview, Mr Powell also dismissed speculation that Saddam Hussein's former deputy, Izzat Ibrahim al-Douri, was linked to the targeting of the American-led forces in Iraq.

The New York Times newspaper had earlier reported that senior US defence officials had intelligence suggesting Saddam Hussein was acting as a catalyst or a leader of armed opposition to the coalition presence.