Twelve coal miners have been killed and 11 others trapped in two gas explosions in China, state media said Monday, in the latest accidents to strike the country's notoriously dangerous mining sector.

The 12 workers were killed in a blast late Sunday at the Donggou coal mine in the city of Jiexiu in northern Shanxi province, Xinhua news agency quoted local authorities as saying.

The accident happened after the workers "violated a safety rule" by demolishing a wall between the shaft and a disused area of the mine where gas had accumulated, a spokesman for the local work safety administration said.

Four people were hospitalised for injuries suffered in the blast, but their condition was unknown, the report said.

In the second incident in southwest Yunnan province's Shuangbai county, rescuers were working to locate 11 trapped workers after a blast at the Malishu coal mine on Monday, Xinhua said.

China's coal mines are among the most dangerous in the world, with safety often ignored in the quest for profits and a drive to meet surging demand for coal, the source of about 70 percent of the country's energy.

Thousands of miners are reportedly killed in accidents every year. Last month, 108 miners were killed in a gas explosion at a coal mine in Heilongjiang province in northeastern China.