Fourteen people died in Shimian county in the city of Yaan, and at least seven others were killed in Luding county, state broadcaster CCTV reported earlier. At least 31 people were injured, with rescue efforts continuing into the night.

A number of main roads, telecoms lines and houses had been damaged and officials were still trying to determine the extent of impact, the county government said.

At least six moderate aftershocks were recorded until 4pm, with more expected, the quake authorities said.

The epicentre was about 40km from the centre of Luding county, home to some 84,000 people, and about 50km from the city of Kangding. Several villages are within a 5km radius of the quake zone, with disaster relief efforts prioritised in Detuo, Moxi and Yanzigou townships.

The leader of the provincial fire services rescue mission, Wei Qing, said his team was working at the Hailuogou park in Moxi township and buildings and roads leading up to the area had sustained structural damage.

Life detection devices had been deployed to locate survivors trapped under collapsed homes, Wei told CCTV.

The average altitude of the quake zone is 2,680 metres (8,790 feet), with an average population density of 22 per sq km, CCTV reported. Nearly 350,000 residents have been affected.

In downtown Shimian, however, it was business as usual for many restaurants and hotels.

“Don’t worry about the earthquake, it wasn’t a big deal,” a staff member of Haowen Barbeque said.

The downtown areas had escaped relatively unscathed, a resident said, adding that it was mainly the rural areas, especially those in the mountains, that had been the hardest hit.

A friend who works in the local government had already joined rescue efforts, she said.

“Some even took a boat [along a river] to the scene [to help out], because roads were damaged by the quake,” she said.

Severe tremors were reported by residents of Chengdu, and the nearby cities of Mianyang and Meishan, where cracks appeared in buildings.

Neighbouring Chongqing municipality and three other provinces – Yunnan, Shaanxi and Guizhou – were also heavily jolted by the quake.

A resident of Lengqi township in Luding said he was nearly knocked off his feet by the tremors. Residents in his neighbourhood escaped to open areas while the walls and floors of several buildings had developed cracks, he told China News Service.

The state news agency also reported rubble piled up on a highway leading to a major bridge towards Luding.

More than 500 rescuers have been sent to the quake zone and a highway sealed off to ensure smooth passage of relief convoys.

Monday’s quake came as the province grappled with challenges on several fronts.

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Panic buying in Chengdu as China locks down another megacity to contain Covid-19 spread

Panic buying in Chengdu as China locks down another megacity to contain Covid-19 spread

Chengdu resident Daphne Zhang said the quake lasted about 30 seconds and was one of the worst she could recall in recent years.

Zhang said her family was under home quarantine, with a siren installed on her door to alert community staff if they tried to step outside.

“We were locked in, and I didn’t dare run outside,” Zhang said.

She said shelves and bottles fell to the kitchen floor as the quake hit, and she ran to the balcony to check if anyone was running out into the open.

“I thought for a minute whether I should run for it,” she said. But the shaking stopped before she had time to think further.

Social media users criticised the strict Covid-19 restrictions in place, saying their fire escapes were blocked, or that community staff would not let those under quarantine run outside to safety.

“Here’s a legal problem that must be solved: when an earthquake strikes, can those under quarantine go outside to avoid imminent danger?” a legal issues blogger wrote on Weibo.

Wang Xiangxi, minister of emergency management and deputy commander of the State Council’s disaster relief arm, is in charge of rescue operations, authorities said.

Min Xiren, head of the China Earthquake Administration, is expected to conduct disaster relief work on-site.

Trains were expected to run late as railway tracks in the quake zone were inspected, China Railway Chengdu Group announced.

President Xi Jinping instructed all-out rescue efforts to minimise casualty figures and any subsequent disasters induced by the earthquake, CCTV reported.

Sichuan, which lies along a major fault line, is among China’s most quake-prone provinces.

Four dead as twin quakes hit Chinese city, site of deadly 2013 shock

More than 1,000 cases have been reported since mid-August in Chengdu alone, a southwestern transport hub of 21 million. Sichuan reported 105 new symptomatic cases on Monday, and another 80 asymptomatic infections.

Additional reporting by Jun Mai