A suicide car bomber has killed five security troops at a road checkpoint in Pakistan's southwest, officials have said.

Murtaza Baig, a government spokesman, said the attacker detonated his explosives early on Saturday after he was stopped at the checkpoint in a Quetta suburb.

The killed troops were members of Pakistan's paramilitary Frontier Corps.

Balochistan province and its capital, Quetta, have been the scene of a rebellion by Baluch nationalists who are demanding greater rights and bigger share of the income generated from gas and minerals extracted from the province.

Various Baloch groups are blamed for attacks on the province's security forces and are suspected of targeting other ethnic groups in the region.

Armed Taliban and Lashker-e-Jhangvi fighters are also active in the province.

US drone strike

Meanwhile, elsewhere in Pakistan, a missile launched by a US drone struck a site in the tribal agency of North Waziristan, killing at least five people, Pakistani officials said.

The intelligence officials said that Saturday's drone strike killed allies of local militia commander Hafiz Gul Bahadur. Three people were also wounded, they said.

The drone fired two missiles on a compound in Shuwedar village in Shawal district of North Waziristan.

The officials spoke on condition of anonymity, because they are not authorised to speak to the media.

Pakistan's foreign ministry has condemned the drone attack.

"Pakistan has consistently maintained that these attacks are a violation of its sovereignty and territorial integrity, and are in contravention of international law," the ministry said in a statement.

Drone attacks are very unpopular in Pakistan, where they are seen as a violation of the country's sovereignty and responsible for the deaths of innocent civilians. The US maintains that the targeted strikes are directed against armed groups only and are necessary to combat groups like al-Qaeda.

Saturday's strike comes as Leon Panetta, the US secretary of defence, told the Associated Press earlier this week that Pakistan was preparing an operation targeting the Pakistani Taliban in North Waziristan.