The tremor was recorded at 12:52 p.m. local time (4:52 a.m. GMT) in Sichuan province, said the United States Geological Survey (USGS) - the world's leading organization for earthquakes.
The depth of the quake is estimated at 10 kilometers and the epicenter is 39 kilometers from Luding County, Chinese state television CCTV said.
A video released by the official New China news agency showed chandeliers swinging from the ceiling, sections of concrete buildings fallen to the ground or rocks blocking a road after landslides.
The tremor was also felt some 200 kilometers further, in the provincial capital Chengdu, whose 21 million inhabitants are currently confined to their homes due to an outbreak of Covid-19.
The first official report of the earthquake reports seven dead, indicated CCTV, which quotes remarks made during a press conference of the authorities of the prefecture of Garze, which administers Luding.
"Houses were seriously damaged" and "telecommunications were cut" in some places near the epicenter, according to the same source.
- Clouds of dust -
The tremor was "relatively strong", told AFP a resident of Chengdu who did not wish to give her full name, Ms. Chen.
“Some of my downstairs neighbors said they felt it very clearly,” she added.
But as Chengdu is currently in lockdown "people are not allowed to leave their residential compounds, so many have rushed to their yards" downstairs from their homes, she said.
Authorities have not reported any damage in the city so far.
Chengdu extended the confinement of its inhabitants on Sunday after the discovery in recent days of hundreds of new positive cases of the coronavirus.
Near the epicenter, telecommunications with Moxi, a small town of 7,000 inhabitants, were cut by the earthquake, indicated the public television CGTN.
A video released by the China Seismic Network Center shows boulders rolling down a hill in Luding Township and kicking up clouds of dust, with telephone lines flickering from the tremors.
More than 500 firefighters and rescue workers have already been dispatched to the epicenter, Xinhua said.
- "Fear" -
The China Seismic Network Center reported several aftershocks in the vicinity of the first earthquake.
A resident of Chongqing, a large municipality-province whose city center is located more than 400 kilometers from the epicenter, told AFP that the tremor was "very clear".
"I was rather scared. But it didn't seem to disturb people here too much," he says.
Sichuan, very mountainous and known worldwide for its panda reserves, is generally hit several times a month by earthquakes of varying intensities.
In June, a 6.1 magnitude earthquake had already shaken the province, killing at least four people and injuring dozens.
In May 2008, a very powerful earthquake, of magnitude 7.9, left 87,000 dead or missing in Sichuan. The disaster was a national shock.
Among the victims were thousands of students killed in the collapse of precariously constructed schools. Police at the time arrested activists who were trying to count the precise number of children who died in the disaster.