Forty deaths were reported from quake-hit areas of Awaran district, chief military spokesman Maj Gen Asim Bajwa said in a message posted on Twitter.
Other officials were quoted by news channels as saying that dozens were injured when mud-brick houses collapsed in Awaran and Khuzdar areas of Balochistan province.
Six bodies were found in Awaran bazar and four more recovered in far flung villages of the district, said Deputy Commissioner Abdul Rasheed Baloch. "I fear more people are trapped inside collapsed houses," he said.
Houses were also damaged in Pasni and Windar but details were awaited from these areas, Baloch said.
More From This Section
The army despatched 300 soldiers, rescue and medical teams and a helicopter to the worst-hit areas. Balochistan Chief Minister Abdul Malik too said an emergency had been declared in Awaran, seven to eight hours' drive from Quetta, the provincial capital.
Both US Geological Survey (USGS) and Pakistan's meteorological office gave the magnitude as 7.7 on the Richter Scale. USGS said five aftershocks measuring between 4.7 and 5.9 were recorded after the quake.
Tremors were felt in Karachi, Hyderabad, Larkana and other towns and cities of Sindh province. Reports said the quake was also felt as far away as Lahore, Rawalpindi and Islamabad.
The tremors that lasted almost a minute caused widespread panic in many places. People rushed out of their offices and homes in Karachi, the country's largest city, and other parts of Sindh and Balochistan provinces.