A missile strike by a suspected US spy drone hit a compound in a Pakistani tribal area bordering Afghanistan, killing four people, security officials said.

The incident on Saturday in the lawless district of North Waziristan, a known haunt of Taliban and al-Qaeda militants, was the latest in a string of attacks on Pakistani soil that have raised tensions between Islamabad and Washington.

"Two missiles struck a compound just outside Miranshah. Four people were killed, but their identities are not known," a security official told AFP on condition of anonymity.

The targeted compound was the residence of Taliban militant Omar Daraz, the official said.

There was no immediate confirmation of the strike from the Pakistani military or from the US-led coalition in Afghanistan.

A similar suspected US missile strike on a house in the same district on Thursday killed nine people including six Arab militants, according to security officials.

Two weeks ago about 20 al-Qaeda-linked militants, mostly foreign nationals, were killed in another suspected US missile strike in Mohammad Khel village in North Waziristan, Pakistani security officials said.

Missile strikes targeting militants in Pakistan in recent weeks have been blamed on US-led coalition forces or CIA drones based in Afghanistan. Pakistan does not have missile-equipped drones.

The United States has stepped up attacks on militants in Pakistani territory since a new civilian government came to power in Islamabad in March, and the incidents have become an issue in the US presidential election.

Relations have also been strained by a raid by US special operations forces into Pakistan on September 3 which killed several Pakistanis.

Pakistani president Asif Ali Zardari has vowed zero tolerance against violations of his country's sovereignty amid the strikes, which have stoked anti-US sentiment in Pakistan.

US and Afghan officials say Pakistan's tribal areas are a safe haven for al-Qaeda and Taliban militants who sneaked into the rugged terrain after the fall of the Taliban regime in late 2001.

Al-Qaeda chief Osama bin Laden and his deputy, Ayman al-Zawahiri, are widely believed to be hiding in the mountainous region.