Around 20 people were killed and more than 200 injured when a shallow earthquake hit southern Pakistan in the early hours of Thursday as people slept, government officials said.

Many of the victims died when roofs and walls collapsed after the 5.9 magnitude quake struck Balochistan, with a power cut forcing health workers to treat the injured using flashlights.

The worst-affected area was the remote mountainous city of Harnai, where a lack of paved roads, electricity and mobile phone coverage hampered rescuers.

Rescue workers said the dead were mostly women and children.

The quake was relatively shallow at 20kms, with an epicentre 102km east of the provincial capital of Quetta, said the US Geological Survey.

https://www.youtube.com/watch?v=ON7EUiEn2fg

More than 100 mud houses collapsed and a large number were damaged, including government buildings.

Many of the victims died when the roofs and walls of their mud-brick houses collapsed after the 5.9 magnitude quake struck Balochistan in darkness at around three in the morning.

It was felt across at least six cities and towns, but the worst-affected area was the remote mountainous district of Harnai, where landslides triggered by the jolt blocked some roads, hampering rescue efforts. 

Authorities are also contending with phone and electricity outages after pylons were damaged.

Social media showed houses shaking and light fittings swaying as the quake struck, and later stunned residents gathering in the street in the dark.

https://twitter.com/occupiedbypak/status/1445936030859739142

https://twitter.com/AamirAliNoonar2/status/1445888844713259009

https://twitter.com/PDMABalochistan/status/1445887846565519360

https://twitter.com/arzakkhan/status/1445881197180043265

The injured were rushed to hospital, while some were treated on stretchers in the street under phone torch light.

"We are receiving information that 20 people have been killed due to the earthquake," Balochistan Home Minister Mir Ziaullah Langau added.

A woman and six children were among 20 dead, Suhail Anwar Hashmi, a senior provincial government official, told AFP, adding that "more than 200 people have been injured".

"We are soon sending helicopters to the area to help support the rescue operation and to evacuate injured," Hashmi said.

"There are reports that some 15 coal miners are trapped in a mine on the outskirts of the town due to the quake," he added.

Army helicopters were helping to evacuate the injured from remote areas to Quetta, the nearest major city. The most serious cases were being sent by ambulance to Quetta. 

"Our rescue teams have cleared 50 per cent of the roads leading to the Harnai while remaining roads will be cleared in the next two to three hours," Balochistan's Home Minister Langau added, highlighting the strain rescue teams were under.

The earthquake was felt in towns throughout Balochistan, which borders Afghanistan and Iran, including provincial capital Quetta, around 170 kilometres west of Harnai. 

It is common in Pakistan for miners to work at night when temperatures are cooler. 

A rescue team was being sent to the mine, while helicopters were due to be dispatched to support the rescue effort and evacuate the injured. 

Naseer Nasar, the head of Balochistan's Provincial Disaster Management Authority, warned that the toll may rise.

The quake caused electricity to fail in the region, with health staff working until dawn without lights in a poorly equipped government hospital.

Before daybreak, "we were operating without electricity with the help of torches and mobile flashlights," Zahoor Tarin, a senior official at the government-run Harnai hospital told AFP.

"Most of the injured came with fractured limbs. Dozens of people were sent back after first aid," he said, adding that "at least 40 people were received with critical injuries".

"We have imposed an emergency in the hospital and are providing them medical treatment."

Private individuals were helping rush the injured to hospitals.

The US Geological Survey said the quake had a magnitude of 5.7 and struck around 3 am at a depth of around 20 kilometres. The earthquake was also felt in Balochistan's capital Quetta.

Pakistan straddles the boundary where the Indian and Eurasian tectonic plates meet, making the country susceptible to earthquakes.

In October 2015, a 7.5-magnitude quake in Pakistan and Afghanistan killed almost 400 people across rugged terrain that impeded relief efforts.

The country was also hit by a 7.6-magnitude quake on October 8, 2005, that killed more than 73,000 people and left about 3.5 million homeless, mainly in Azad Kashmir.–Agencies