CHENGDU, CHINA - Thirty-seven tourists were killed when their coach was buried by a landslide after a catastrophic earthquake hit China, state media said Tuesday, adding another 2,000 are unaccounted for.

The tourists were travelling in Sichuan province in southwest China when the devastating quake struck, the official Xinhua news agency said, quoting local emergency authorities.

An estimated 2,000 travellers remained unaccounted for in the wake of the 7.9-magnitude quake, including at least 15 British tourists believed to be stranded in the disaster zone of Wenchuan county in Sichuan, Xinhua said.

The British tourists were probably in Wolong, home to a famed giant panda centre, said a spokesman for the provincial emergency management office.

The region is home to the endangered animals, and the Wolong panda park is one of China's biggest tourist attractions.

The British Embassy in Beijing said it had sent four emergency workers to Chongqing to assess the situation of its nationals in the area.

"At the moment, we have little idea about the latest situation of the area. Hopefully, we will be able to find out more this afternoon," a spokesman told AFP.

Australia's foreign ministry said it was contacting its nationals in the affected areas to confirm their safety.

"We have a very small number of people registered as being in the area - residents, people working on short-term contracts with volunteer programmes and the like," a spokeswoman told AFP.

"The problem is that people don't register, so the number is getting bigger and bigger as we get calls from relatives to let us know they have family in the area," she said.

Ailsa Weymes, a teacher accompanying more than 100 Hong Kong students on a week-long trip to China, said they were driving to a panda park near Chengdu when the quake hit.

The group initially blamed the roads or poor driving for the shaking vehicle, only later realising they had been thrown around by the force of the quake, she said.

She said she was kept awake all Monday night as aftershocks shook tables, lights and the floor.

The group planned to fly to Xian in central China after authorities indicated some flights could resume Tuesday afternoon, she said.

A Hong Kong government spokeswoman said a 60-year-old Hong Kong woman had suffered a serious head injury during the quake and had undergone surgery, but gave no further details.

Two major travel agencies in Hong Kong, China Travel Service and Hong Thai Travel, said their tour groups in or near Sichuan had been located and were safe.

Joseph Tung, executive director of the Travel Industry Council in Hong Kong, said he had not received any reports of injury or deaths from Hong Kong tour groups in the disaster zone.

Five flights between Hong Kong and Chengdu were either delayed or cancelled on Tuesday, a spokeswoman for the Airport Authority in Hong Kong told AFP.