Islamabad - The official death toll from the devastating earthquake that hit south-western Pakistan a day ago climbed to more than 230 as the rescue workers searched for entombed survivors, officials said on Thursday.

Many of the around 20,000 people left homeless spent the freezing night in the open as a series of mild aftershocks struck the northern parts of Balochistan province that was rattled by a magnitude 6.4 earthquake just before dawn on Wednesday.

Various hospitals have received 149 bodies so far while 89 people were buried by the locals, Urdu-language Geo news channel cited provincial police chief, Asif Nawaz Warraich, as saying.

Warraich feared that the death toll might rise even further.

Locals assisted by government troops and paramilitary forces searched the rubble of flattened mud houses for survivors amid grim hopes of pulling anyone out alive more than 24 hours after the devastation.

"After initial rescue efforts, we are now prioritizing our operations to focus on the worst affected areas," said Major General Asif Nawaz, regional head of the Frontier Corps paramilitary force.

Balochistan's Ziarat district was the hardest hit being closet to the epicentre of the shallow earthquake whose depth was just 10 kilometres.

Nawaz said his troops were reaching out to the homeless people who were not leaving the site of their demolished huts. "We want them to relocate to tent villages set up to save them from the extreme chill," he added.

Temperatures in the region dropped below freezing point through the night.

"Forecast for next few days is partly cloudy but the mercury is likely to fall further," Pakistan Meteorological Department Director General Qamaruz Zaman Chaudhry said.

The World Health Organization (WHO) has listed exposure to cold weather among the major health concerns facing the at least 20,000 homeless people.

It said accessibility of the displaced people to health services and safe food and water would be a challenge for the authorities.

WHO is coordinating with Pakistani agencies in the medical response and is also flying trauma supplies stored at the United Nations Humanitarian Response Depot in Dubai to treat 400 people into the region.

United Nations offices have also sent a joint assessment team to Ziarat and Pishin, the two districts greatly affected by the earthquake.

Military aircraft are making sorties to deliver tents, medicine and blankets to the far-flung villages devastated by the strong jolts.

Scores of injured people have poured into hospital but are camping outside the brick and concrete buildings, with fearful memories of Wednesday's quake. Authorities have pitched tents to accommodate those refusing to stay indoors.

Several countries and the European Union have offered assistance to Pakistan following the earthquake, however, Islamabad has so far not made any formal request terming the incident "localized."

A massive earthquake measuring 7.6 on the Richter scale struck Kashmir and Pakistan's mountain region in October 2005 and prompted the country to seek international help to recover from the disaster. The earthquake killed at least 73,000 people and left 3.5 million others homeless.