A US missile strike targeting a militant vehicle killed four rebels on Thursday in the second drone strike in 48 hours to hit Pakistan's tribal region, local security officials said.

A drone strike on Tuesday signalled apparent resumption of the covert CIA campaign after a two-month lull to avoid a worsening of US-Pakistan relations after a NATO raid that killed 24 Pakistani soldiers, infuriating Islamabad.

The latest missiles struck in the New Adda area, 30 kilometres (18 miles) west of Miranshah, the main town of the North Waziristan tribal region.

"US drones fired four missiles targeting a rebels' vehicle and killing four militants," a local security official told AFP on condition of anonymity because he was not authorised to speak to media.

Another security official confirmed the strike and casualties. He said the identities of those killed were not immediately known.

On Tuesday two missiles struck a compound, also in the outskirts of Miranshah, in the first such strike since November 17. Four people were killed.

The US drone campaign has reportedly killed dozens of Al-Qaeda and Taliban operatives and hundreds of low-ranking fighters in the remote areas bordering Afghanistan since the first Predator strike in 2004.

But the programme fuels widespread anti-American sentiment throughout Pakistan, which has been especially high since the deadly NATO incident on November 26.

A joint US-NATO investigation concluded last month that a catalogue of errors and botched communications led to the soldiers' deaths. But Pakistan rejected the findings, insisting the strikes had been deliberate.

NATO's probe said that both sides failed to give the other information about their operational plans or the location of troops and that there was inadequate coordination by US and Pakistani officers.

The incident prompted Islamabad to block NATO supply convoys heading to Afghanistan and order the United States to leave Shamsi air base in western Pakistan, from where it is believed to have launched some of its drones.

Others are flown from within Afghanistan.

The region had served as the main supply route for NATO forces operating in Afghanistan before the suspension triggered by the November incident.