The 7.7-magnitude quake struck on Tuesday afternoon in Baluchistan province's Awaran district - a dirt-poor expanse of land that is roughly the size of Wales.
Officials said 238 deaths had been confirmed so far, 208 in Awaran district, and the toll is expected to rise as rescue teams reach more villages in the remote area.
"A total of six districts - Awaran, Kech, Gwadar, Panjgur, Chaghi and Khuzdar - and a population of over 300,000 have been affected by the earthquake," said Jan Muhammad Buledi, spokesman for the Baluchistan government.
The head of the provincial disaster management agency, Abdul Latif Kakar, says 30 people had died in Kech district, a toll confirmed by a senior local official.
Buledi said teams were working to recover bodies, but the priority was to move the injured to hospitals as soon as possible - a difficult task in a desolate area with minimal infrastructure.
The army has sent 100 medical staff and 1000 troops to the area to help with rescue efforts and has established a medical centre in one of the worst-affected villages, Tarteej.
The scale of the territory involved is daunting. Awaran's population is scattered over an area of more than 21,000 square kilometres. A new island appeared after Tuesday's quake close to the Pakistani coastline at Gwadar, officials say.
"The island, which is up to 100 feet high (30 metres) and 200 feet wide, surfaced after the earthquake hit parts of Baluchistan," senior local administration official Tufail Baluch said.
He said a similar island had appeared at the same place in the sea about 60 years ago but disappeared after some time.
The US Geological Survey issued a red alert on Tuesday, warning that heavy casualties were likely based on past data, and the provincial government declared an emergency in Awaran.
Television coverage 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.
