MIRAMSHAH, Pakistan: A US drone strike killed four militants in northwestern Pakistan on Friday, the third such attack in 48 hours against Taliban hotbeds in Waziristan near the Afghan border, officials said.

The drone fired two missiles into a vehicle as it drove through Darpa Khel village about four kilometres (two miles) west of Miramshah, the main town in the district of North Waziristan, the Pakistani security officials told AFP.

“The US drone fired two missiles,” one of the officials told AFP on condition of anonymity because he was not authorised to talk to the media.

“Four militants were killed in the attack, they were all in the vehicle,” he added.

The identities of the dead were not clear, but the village is a stronghold for militants fighting against US troops in Afghanistan.

Covert CIA drones are the chief US weapon against Taliban and al Qaeda militants who use Pakistan's lawless tribal areas as launchpads for attacking US troops in Afghanistan and plotting attacks on the West.

A US official in Washington described a commander in the al Qaeda-linked Haqqani network who was killed on Thursday as “the most senior Haqqani leader in Pakistan to be taken off the battlefield”.

Pakistani officials reported 10 militants killed in two US drone strikes on Thursday and named the Haqqani commander as Jamil Haqqani, a coordinator for the Afghan Taliban faction in North Waziristan.

The US official said he was known as Jamil and as Janbaz Zadran, accusing him of having “played a central role in helping the Haqqani network attack US and coalition targets in Kabul and southeastern Afghanistan”.

Pakistani officials said the slain commander was not a relative of Jalaluddin Haqqani, the Afghan warlord who founded the Taliban faction, but had been close to his son Sirajuddin Haqqani, who now runs the network.

The United States blames the Haqqanis for fuelling the 10-year insurgency in Afghanistan, attacking US-led Nato troops and working to destabilize the Western-backed government of Afghan President Hamid Karzai.

The US military has accused Pakistan's premier intelligence outfit, the ISI, of having close ties to the network and of being involved in a 19-hour siege of the American embassy in Kabul on September 13.

After that attack, which killed 14 Afghans, Washington significantly stepped up demands on Pakistan to take action against the Haqqani network.

But Pakistan has refused to launch a sweeping ground offensive in North Waziristan, the Haqqanis' leadership base, leaving American response largely limited to US drone strikes.

More than 50 have been reported in Pakistan so far this year including dozens since Navy SEALs killed al Qaeda leader Osama bin Laden in the garrison city of Abbottabad, close to the capital Islamabad, on May 2.

Defence Secretary Leon Panetta has said for the first time that the United States was waging “war” in Pakistan against militants, referring to the covert CIA drone campaign that Washington refuses to discuss publicly.