Islamabad - A powerful earthquake rattled Pakistan's south-western Balochistan province on Wednesday, killing up to 140 people and injuring scores of others, officials said.

The US Geological Survey website said a magnitude 6.4 earthquake struck 60 kilometres north-east of Quetta, the capital of Balochistan at 5:10 am (2310 GMT).

People fled their houses in panic as the shocks hit Balochistan just before sunrise, while television footage showed terrified families wrapped in blankets sitting by the roadsides in Quetta.

Ahmadullah, a local official in the most severely affected district of Ziarat, said about 140 people had died in Wam village alone.

More than 2,000 houses were destroyed or badly damaged in the entire district, about 50 kilometres from Quetta, he told Deutsche Presse-Agentur dpa by telephone.

Provincial Minister for Revenue and Rehabilitation Zmarak Khan said initial information showed more than 100 people had died.

He feared the death toll might rise as many people were trapped under demolished houses.

At least five more people died in Pishin and Khoshab areas.

Pakistan Meteorological Department Director General Dr Qamaruz Zaman Chaudhry described the tremor as a shallow earthquake, at a depth of about 10 kilometres.

"A shallow earthquake of this magnitude is normally very destructive," he said.

Officials were trying to assess the extent of the damage in Balochistan, which is Pakistan's largest but most sparsely populated province.

Relief workers had only reached villages located close to main roads, while many remote areas were inaccessible.

The earthquake also triggered mudslides that blocked roads and hampered relief work. Military helicopters were flown to the area.

Major General Asif Nawaz, regional head of the paramilitary Frontier Corps, said troops had established camps for relief operations.

Twenty-two severely injured people were moved to two hospitals in Quetta and more were being transported.

Balochistan was also struck by a magnitude 7.3 earthquake in 1997 which killed more than 100 people. The worst earthquake hit the province in 1935, killing more than 30,000 people and almost flattening the entire Quetta city.

On October 8, 2005, a massive earthquake measuring 7.6 on the Richter scale shook Kashmir and Pakistan's mountain region, killing at least 73,000 people and leaving 3.5 million others homeless.