The police and National Guard were attacked by rebel mortar fire and rocket-propelled grenades as they provided security to US forces conducting raids near the rebellious town of Buhriz, 55 km (35 miles) north of Baghdad, the US military said.

During the fighting yesterday, which lasted around an hour, US warplanes patrolled the skies and US artillery guns opened fire to suppress the insurgents' mortar positions, Major Neal O'Brien of the US 1st Infantry Division said.

It was one of the first major battles between Iraq's security forces and insurgents since the handover of sovereignty on June 28 and by far the largest death toll. No Iraqi security forces or US troops were killed.

The fighting came as Iraq's months-long hostage crisis took another turn for the worse -- two Pakistanis working for a Kuwait-based company were feared kidnapped after going missing.

Pakistan's Foreign Office said the two, an engineer and a driver believed to be working for the al-Tamimi Group, disappeared on Friday as they drove to Baghdad.

"We are trying to find out the details. It is feared they have been kidnapped," a Foreign Office spokesman said. "We will try our best to get them released if they are kidnapped."

Over the past 15 months, nationals from nearly two dozen countries have been kidnapped in Iraq, sometimes by criminal gangs, but increasingly by militants seeking to put pressure on governments and foreign companies to pull out of the country.

In a step up in sophistication for militants, a senior Egyptian diplomat was seized as he left a Baghdad mosque on Friday. Most of those kidnapped so far have been drivers.

Abductions have sharply increased since April, when several dozen people were seized in one month. Around 60 people have been taken hostage since then, officials say.

Although most have since been freed, at least six have been killed -- four of them by beheading -- and on at least two occasions the hostage-takers' demands have been met, a move that may be fuelling the surge in abductions.

The seizure of the Pakistanis came as a group calling itself al Qaeda's arm in Europe said Italy and Australia, both strong allies of the United States, must pull out of Iraq or face attacks at home, while Iraq's interim Prime Minister Iyad Allawi urged nations not to give in to terrorists.

Meanwhile, a US soldier was killed when a roadside bomb struck his convoy near the northern Iraqi oil refinery town of Beiji, the US military said yesterday.

The soldier with the 1st Infantry Division died of his injuries and another was wounded after their convoy was attacked Saturday near Beiji, some 200km from Baghdad, the military said in a statement.

The latest death brings to almost 670 the number of US troops killed in Iraq since the March 2003 launch of the US-led invasion that ousted president Saddam Hussein, based on Pentagon figures.