At least nine people have been killed and nine others trapped in mining and tunnel building accidents in China.

The official Xinhua News Agency says nine miners were killed in a gas explosion deep inside the shaft on Wednesday afternoon in the northeastern province of Heilongjiang. Eight others were rescued and taken to hospital.

Separately, Xinhua says nine workers were trapped when a railway tunnel they were working on collapsed on Thursday morning in the southwestern province of Yunnan.

China's mines were long the world's deadliest, although steady improvements in regulations, safety training and equipment have reduced the toll. China is the world's biggest producer and consumer of coal.

Accidents on construction sites remain common, sometimes caused by the cutting of corners in a rush to meet completion deadlines.