An earthquake hit a mountainous area of southwest China on Sunday, killing at least four people and injuring more than 100, state media reported.

The US Geological Survey (USGS) said the quake had a magnitude of 5.5 and struck the border between the provinces of Sichuan and Yunnan just before 4:00 pm (0800 GMT), at a shallow depth of just 9.3 kilometres (5.8 miles).

The Chinese government put the magnitude of the quake at 5.7. It was followed two minutes later by an aftershock of 3.3, the China Earthquake Network Centre said.

The quake toppled houses and cut off communications with parts of Ninglang county in Yunnan, the official Xinhua news agency said.

The tremor killed three people in Ninglang while another one was reported dead in neighbouring Yanyuan county in Sichuan.

A total of 104 were injured in the quake with 20 in serious condition, Xinhua said, quoting local authorities.

Yunnan provincial authorities had sent relief supplies to Ninglang, where the quake was strongly felt, including 1,100 tents and 3,000 quilts, it said. The province had also sent a team to the area.

An official in the historic city of Lijiang, which administers Ninglang, told AFP it was too early to have detailed estimates of casualties and damage.

Separately, a Yanyuan county government official was quoted by Xinhua as saying that "many" houses in rural areas had collapsed, but he gave no figure.

"I felt it, but I don't know about casualties," another official of the Yanyuan civil affairs bureau told AFP, adding that the government was trying to calculate the casualties.

The area is inhabited by the Yi ethnic minority. China estimates there are around 7.8 million Yi people living in four provinces, including Yunnan and Sichuan.

The remote and mountainous region regularly suffers quakes. A powerful earthquake hit Lijiang, a UNESCO world heritage site, in February 1996, killing 200 people and destroying thousands of mud-walled homes.

An 8.0-magnitude quake rocked Sichuan province on May 12, 2008, killing tens of thousands and flattening swathes of the province.