At least 21 people have been killed after a 6.6 magnitude earthquake hit southwestern China, state media said.

The quake struck at 13:00 local time (05:00 GMT) in Sichuan province at a depth of 10km (6 miles).

The impact severed telecommunications lines and triggered mountain landslides that caused "serious damage", local media reports say.

Some 21 million people in Sichuan's capital Chengdu were earlier ordered to stay home because of Covid rules.

The epicentre of the quake was at Luding, a town in a remote mountain region located about 226km southwest of Chengdu, according to the China Earthquake Networks Centre.

Tremors shook buildings in Chengdu and the neighbouring mega-city of Chongqing, leaving roads blocked and cutting telecommunications lines in areas home to more than 10,000 residents, according to broadcaster CCTV.

The shocks also forced some power stations to shut down in the areas of Garze and Ya'an, the Chinese broadcaster said.

More than 500 rescue personnel have been despatched to the epicentre, while workers laboured to clear roadblocks caused by landslides, according to state broadcaster CGTN.

Chengdu residents reported seeing people running out of their high-rise apartments in a panic after receiving earthquake alerts on their phones.

"There were many people who were so terrified they started crying," Laura Luo, an international PR consultant, told news agency Reuters.

When the shaking began, "all the dogs started barking. It was really quite scary".

"Some of my neighbours on the ground floor said they felt it very noticeably," Chen, a resident of Chengdu, told AFP news agency.

"But because Chengdu is currently under epidemic management, people aren't allowed to leave their residential compounds, so many of them rushed out into their courtyards."

Chengdu is the latest city to be locked down by Chinese authorities on Friday, in an attempt to stem the rise in Covid cases.

The latest disaster comes months after a 6.1-magnitude earthquake tore through Sichuan in June. Sichuan is a earthquake-prone area, as it lies along the eastern boundary of the Qinghai-Tibetan plateau.

The latest disaster also called into memory an 8.0-magnitude quake which hit Wenchuan county in northwest Sichuan in 2008, which killed 70,000 and caused widespread destruction.