The CIA-operated spy plane fired missiles at the vehicle in Barmal area of South Waziristan Agency, where the Pakistan Army had conducted a major offensive to flush out militants three years ago. The identity of the dead men could not immediately be ascertained. There have been about a dozen drone attacks in Pakistan's tribal belt this year.
At least 40 people were killed in these missile strikes, most of which were carried out in North Waziristan Agency. Al-Qaeda recently confirmed that a strike in North Waziristan last month killed military commander Badr Mansoor, accused of being a mastermind of many suicide attacks.
Following a spike in tensions between the US and Pakistan in the wake of the American raid that killed Osama bin Laden, the number of drone attacks dropped last year.
The use of the CIA-operated spy planes was cut back further after a cross-border NATO air strike killed 24 Pakistani soldiers in November. Pakistani officials publicly describe the missile attacks as "counter-productive" but reports have said the government has extended tacit support to the drone campaign.