Pakistani intelligence officials say a suspected U.S. drone strike has hit a vehicle in a tribal region near the Afghan border, killing at least six militants.

The officials say two drone-fired missiles hit the militants' vehicle in Wakdalai village of South Waziristan's Birmal area on Tuesday. The officials spoke on condition of anonymity because they are not authorized to speak to media.

The Pakistani military has tried to clear South Waziristan of militants but they still have sanctuaries in the mountainous region.

Islamabad criticizes the drone strikes publicly but the government is widely believed to have supported the covert CIA-run program. That cooperation has come under strain as U.S.-Pakistani relationship has deteriorated.