The 7.7-magnitude quake struck at 4:29 pm (1129 GMT) around 100 kilometers southwest of the city of Khuzdar in Baluchistan province, at a depth of 15 kilometers.
Officials said the tremors had demolished dozens of houses in Awaran district, 350 kilometers southwest of the provincial capital Quetta.
The area of the epicenter is sparsely populated and most buildings are mud-built, but the US Geological Survey issued a red alert for the quake, warning that heavy casualties were likely based on past data.
Top local administration official Akbar Haripal told AFP that eight bodies have been recovered and 24 people were injured in different areas of Awaran.
"A large number of houses have collapsed in the area and we fear the death toll may rise," said Rafiq Lassi, police chief for Awaran district.
The provincial government has declared an emergency in Awaran and the military has mobilized 200 soldiers and paramilitary troops to help with the relief effort.
"We have received reports that many homes in Awaran district have been collapsed. We fear many deaths," Jan Muhammad Baledi, a spokesman for the Baluchistan government, said on the ARY news channel.
"There are not many doctors in the area but we are trying to provide maximum facilities in the affected areas."
Television footage showed collapsed houses, caved-in roofs and people sitting in the open air outside their homes, the rubble of mud and bricks scattered around them.
Tremors were felt as far away as New Delhi, while office workers in the Indian city of Ahmedabad near the border with Pakistan ran out of buildings and into the street in panic.
Abdul Qudoos Bizinjo, deputy speaker of Baluchistan's assembly, told Dunya TV there were reports of "heavy losses" in Awaran. Damage to the mobile phone network was hampering communications in the area, he said.
Awaran district has an estimated population of around 300,000.
In April a 7.8-magnitude quake centred in southeast Iran, close to the border with Baluchistan, killed 41 people and affected more than 12,000 on the Pakistan side of the border.
Office workers in Pakistan's largest city Karachi rushed out of their buildings, and squatted or stood on the footpaths well away from the structures.
"My work table jerked a bit and again and I impulsively rushed outside," Noor Jabeen, a 28-year woman working for an insurance company said, breathing heavily.
"It was not so intense but it was terrible," said Owais Khan, who works for a provincial government office.
"Whenever I feel jolts it reminds me of the 2005 earthquake in Kashmir," said Amjad Ali, 45, an IT official standing in the street.
A 7.6 magnitude quake in 2005 centered in Kashmir killed at least 73,000 people and left several million homeless in one of the worst natural disasters to hit Pakistan.
SHI/SHI