At least four people have been killed and over 100 others injured after an earthquake hit a mountainous area in southwest China on Sunday, local authorities announced on Monday.

The magnitude-5.7 quake, which struck the border of Yunnan and Sichuan provinces at 3:59 p.m., killed three people in Ninglang county of Yunnan and another person in Sichuan's Yanyuan county.

It was followed by 53 aftershocks, with the strongest measured at magnitude 3.8, said Chen Qin, deputy head of the Yunnan provincial seismology bureau.

As of 2 a.m. Monday, 106 people, including seven tourists, have been found injured in Ninglang. Twenty of them suffered severe injuries, said He Lianghui, mayor of the city of Lijiang, which administers Ninglang.

The quake has toppled over 4,280 houses and cut roads and water supplies in the county, disrupting the lives of more than 21,800 people, added He.

A quake relief center has been set up and a team of 1,300 rescue workers has been dispatched to the region, according to the city government.

Provincial and city authorities have sent relief supplies, including 2,000 tents, 3,000 coats, 3,000 quilts, bottled water and food to Ninglang.

The Yunnan Provincial Civil Affairs Department sent an additional 1,000 tents to Ninglang on Monday to guard against possible rainfall, as the county has entered its rainy season.

The Yunnan Provincial Department of Finance has set up a disaster relief fund totaling 5 million yuan (785,625 U.S. dollars) for the quake-stricken area.

In Yanyuan county in Sichuan, one villager has been found dead in the earthquake's aftermath. And 48 injured people, including three in serious conditions, have all been sent to hospital, said authorities with the county's disaster-reduction bureau.

Two work teams sent by the Sichuan Seismological Bureau have discovered several cave-ins and seriously affected sites in the quake-hit area, according to the bureau.

Local residents affected by the quake have been relocated to temporary shelters.

Disaster relief goods, including tents, foods and quilts, have been sent to the disaster-affected region.