MIRANSHAH: A series of unmanned US drone strikes in a lawless district of Pakistan on Sunday killed at least 13 militants, officials said, as tribesmen took to the streets to protest the aerial campaign.

The first two attacks took place in Datta Khel, some 40 kilometres (25 miles) west of North Waziristan's main town of Miranshah. The third was in Mando Khel, around 60 kilometres south of the town.

In the first strike two missiles were fired on a vehicle seconds after it stopped outside a house in Datta Khel, officials said.

“The US drone hit a car immediately after it parked outside a house. Four militants have been killed,” an intelligence official in Miranshah told AFP, adding that the vehicle was destroyed and the house badly damaged.

“Preliminary reports said all of them were local militants but we are trying to get more information,” he added.

A second intelligence official said the drone fired two missiles.

An intelligence official in Peshawar also confirmed the attack and the number of missiles, saying: “At least four militants have been killed.”Another US drone then fired two missiles at a motorcycle travelling in the same town, killing three militants, local officials said.

“Three militants have been killed in the second attack,” a security official in Miranshah told AFP.

Another security official said the militants were riding a motorcycle when they were hit by the US drone.

It was not immediately clear if the drones were pursuing any high value target but one intelligence official in Miranshah said they were checking reports that a foreigner was among those killed in the second attack.

In the third strike, a vehicle parked inside a suspected militant compound was hit.

“A US drone was chasing a vehicle, it fired two missiles just after the car was parked. Six militants have been killed and three injured,” an intelligence official in Miranshah said.

The area close to the Afghan border is a key battleground in the fight against the Taliban and Al-Qaeda.