Image caption The announcement did not specify which industries would be affected by the new rules

The Chinese government has ordered firms in heavy-polluting industries to cut emissions by 30% by 2017.

Under the new rules companies will be legally obliged to improve their pollution control equipment and will be penalised for excess emissions.

Analysts said enforcement of the targets was likely to fall to local governments.

The announcement did not specify which industries would be affected by the new emissions rules.

However, earlier this year ministers hinted that industries such as iron, steel, petrochemicals and cement would face new targets.

China has seen scores of environmental protests.

Protests

The State Council announced the emissions targets as part of a document that approved 10 measures for tackling environmental problems, including:

Curbing the growth of energy-consuming industries like steel, cement, aluminium, and glass

Refusing permission for new industrial projects if they failed to meet required standards

Strengthening enforcement of the current penalties regime

Some of the biggest and most successful recent protests in China have been triggered by environmental concerns.

In 2007, residents of Xiamen staged a series of protests against the construction of a chemical factory in the area and forced the local government to back down.

And anger over air pollution in Beijing, expressed mainly in online forums, led the local government to change the way in which it monitored pollution levels.