A magnitude-6.2 earthquake jolted a remote and mountainous county on the northern edge of the Qinghai-Tibetan plateau around midnight on Tuesday, killing at least 111 people and injuring more than 230, according to Chinese state media.

The quake struck Jishishan county in China's northwestern province of Gansu at 11:59 p.m. local time (1559 GMT) on Monday at a depth of 10 km (6.2 miles), according to China Earthquake Networks Center (CENC).

Rescue and relief efforts are under way and a working group has been dispatched to assess the impact of the disaster, state media said, with the number of missing people in the quake's aftermath unknown.

Earthquakes are common in western provinces such as Gansu, which lie on the eastern boundary of the Qinghai-Tibetan plateau, a tectonically active area. China's deadliest quake in recent decades was in 2008 when a magnitude-8.0 temblor struck Sichuan, killing nearly 70,000 people.

The epicentre of the latest quake was 5 km from the border between Gansu and a neighbouring province. Strong tremors were felt in many parts of Qinghai province, the official Xinhua news agency said.

About 2,200 rescue personnel from the provincial fire department and forest brigade as well as professional emergency rescue teams were dispatched to the disaster zone, Xinhua reported, adding that the military and police were also engaged in rescue work.

China's national commission for disaster prevention, reduction and relief and Ministry of Emergency Management have activated a level-IV disaster relief emergency, Xinhua reported.

As the disaster area is in a high-altitude region where the weather is cold, rescue efforts are working to prevent secondary disasters caused by factors beyond the quake, Xinhua said.

The temperature in Linxia, Gansu, near where the quake occurred, was about minus 14 degrees Celsius (6.8°F) on Tuesday morning. Most of China is grappling with freezing temperatures as a cold wave that started last week continued to sweep through the country.

Some water, electricity, transportation, communications and other infrastructure have been damaged but officials provided no further details.

Power to the quake-hit area was being gradually restored, after the state grid sent 18 emergency repair teams, state television CCTV said.

Videos and photos on social media showed rubble around collapsed buildings and residents standing in open spaces in the dark, some huddled in thick blankets.

Woken up by the quake, residents left their buildings and drove out to open areas for safety, local media outlet Jimu reported.

At a university in Gansu, students dressed in down jackets were seen lingering in groups outside their dormitory after the quake, a video posted by state-backed The Paper showed.

Preliminary analysis shows that the quake was a thrust-type rupture, one of three above magnitude 6 to have struck within 200km of the epicentre since 1900, CCTV said.

A total of nine aftershocks at magnitude 3.0 and above were recorded by Tuesday morning, two of which were at least 4.0 in magnitude, CENC said.