At least six people, including three foreign Islamist militants, were killed in a suspected U.S. missile strike on Monday in a Pakistani region known as a safe haven for al Qaeda, intelligence officials and residents said.

The attack took place near Azam Warsak village, about 20 km (12 miles) west of Wana, the main town of the South Waziristan tribal region bordering Afghanistan.

"At least three missiles struck the house at around 4:00 a.m. (6:00 p.m. British time), killing six people and wounding three," an intelligence official in the region said.

Another intelligence official, who declined to be identified, said the dead included three foreigners and three local tribesmen.

Residents said they heard the sound of a drone aircraft engine, suggesting that the missile may have been fired by a U.S.-controlled unmanned Predator.

"We had heard the sound of a drone engine just before the explosions," said Zia-ur-Rehman, a local tribesmen.

"These drones have been flying since late Sunday night."

A Pakistani military spokesman said he had little information.

"Some incident did take place but what kind of strike it was, whether it was missile or rocket attack or bomb explosion, we don't know," said military spokesman Major General Athar Abbas.

"Coalition forces don't share information about any strike with us prior to any attack," he said.

Pakistani Prime Minister Yousaf Raza Gilani was in Washington on Monday and due to hold talks later with President George W. Bush that will focus on the conduct of the war against terrorism. Drone missile strikes have killed dozens of suspected militants in northwest Pakistan this year.

Security in northwest Pakistan has deteriorated in the past few weeks.

Pakistani Taliban chief Baitullah Mehsud, whose fighters were blamed for many of the suicide bomb attacks on Pakistani security forces and politicians last year, has suspended peace talks and threatened to unleash a fresh wave of violence.

There had been a lull in the violence since the new government came to power in March after elections in February.

Gilani's government embarked on a strategy of dialogue with the militants, although there has been limited military action in some parts of the semi-autonomous tribal region where unrest has flared.

Western governments with troops in Afghanistan have been alarmed by a spike in attacks on their forces, and the flow of fighters across the border fuelling the Afghan insurgency since Pakistan began talking with militants.

Separately, a bomb planted on a bicycle killed a boy and wounded eight policemen near the northwestern garrison town of Kohat on Monday, police said. The policemen had been aboard a bus taking them on duty when the remote-controlled device exploded.