At least 12 people died as a result of a carbon monoxide leak at a coal mine in the northeastern Chinese province of Heilongjiang, the official Xinhua news agency reported Wednesday.

Three other workers were rescued and are listed in good condition, while some rescue team members also were reportedly affected by the toxic gas.

Seven miners were taken out of the mine alive and rushed to a hospital but they did not respond to medical treatment. It is not known if other miners remain trapped.

Ten were killed and 28 were injured two weeks ago in a similar carbon-monoxide leak at a mine in the Chinese province of Jilin, Xinhua reported then.

Chinese coal mines are the most dangerous in the world, with around 3,000 deaths occurring annually due to lack of safety measures and cave-ins caused by overexploitation.

Coal supplies between 60 percent and 70 percent of the energy needs of the world's second-largest economy. EFE