Rescue workers search for survivors in collapsed buildings at the epicenter of an earthquake that struck China Sunday afternoon. Authorities said about 400 people were killed in the quake, more than 1,800 were injured and about 12,000 homes collapsed.

KUNMING, China — Rescuers dug through shattered homes today looking for survivors of a strong earthquake in southern China’s Yunnan province as the death toll rose to at least 398 people, with more than 1,800 injured.

About 12,000 homes collapsed when the quake struck Sunday afternoon in impoverished Ludian county. Overhead footage of the quake zone shot by state broadcaster CCTV showed older houses flattened but newer multistory buildings still standing.

The magnitude-6.1 quake struck at 4:30 p.m. Sunday, according to the U.S. Geological Survey.

Rain and thunderstorms were forecast for the area this afternoon, complicating efforts to bring tents, water, food and other relief supplies to survivors. Roads had caved in, and rescuers were forced to travel on foot.

Repeated aftershocks also were making the rescue work dangerous. The USGS showed four aftershocks of magnitude 4.5 and higher hitting after the initial quake.

Many of the homes that collapsed in Ludian, which has a population of about 429,000, were old and made of brick. Electricity and telecommunications were cut off. The mountainous region is largely agricultural, with farming and mining the top industries, and is prone to earthquakes.

Relief efforts are under way, with more than 2,500 troops dispatched to the disaster region. The Red Cross Society of China allocated quilts, jackets and tents for those made homeless by the quake, while Red Cross branches in Hong Kong, Macau and neighboring Sichuan also sent relief supplies.

Chinese Premier Li Keqiang reached the worst-hit area this afternoon to oversee quake relief, Xinhua said.

CCTV said the quake was the strongest to hit Yunnan in 14 years.

In 1970, a magnitude-7.7 earthquake in Yunnan killed at least 15,000 people, and a magnitude-7.1 quake in the province killed more than 1,400 in 1974. In September 2012, 81 people died and 821 were injured in a series of quakes in the Yunnan region.

In May 2008, a powerful quake in Sichuan province left nearly 90,000 people dead or missing.