Two missiles fired by the drone hit the vehicle in Azam Warsak, 15 kilometres (nine miles) west of Wana, the main town of the South Waziristan region, where Pakistani troops has been fighting militants for two years.
"At least four militants were killed in the strike," a local security official told AFP.
The latest US drone attack was the first since July 12, when missiles hit a compound and a vehicle in the neighbouring North Waziristan tribal region, killing at least six militants.
The United States does not officially confirm Predator drone attacks, but its military and the CIA operating in Afghanistan are the only forces that deploy the armed, unmanned aircraft in the region.
More than 20 US drone strikes have been reported in Pakistan since May 2, when US elite forces killed Al-Qaeda chief Osama bin Laden, who was found living near Pakistan`s main military academy.
The raid humiliated the Pakistani military and prompted allegations of incompetence and complicity in sheltering bin Laden.
Drone attacks are unpopular among the Pakistani public, which is opposed to the government`s alliance with Washington and sensitive to perceived violations of sovereignty.
Another security official in the area confirmed Monday`s strike and casualties, but said the identities of those killed were not immediately known.
The semi-autonomous tribal areas of Pakistan are home to various Islamist militant groups, including the Taliban and other insurgents who operate across the border in Afghanistan. (*)
Editor: Kunto Wibisono
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