BEIJING - China is moving to tighten control over pollutant emissions from new motor vehicles.

A recently revised policy demands stricter emission limits to be gradually placed on carbon monoxide, total hydrocarbons, nitrogen oxides and particulate matter produced by new motor vehicles, according to a Ministry of Environmental Protection statement Wednesday.

The ministry will make unified national emission standards for new vehicles, with local authorities encouraged to adopt the standards ahead of schedule. Priority of regulation will be put on heavy-duty diesel vehicles.

Authorities will encourage the research and development of automobiles using alternative fuels such as natural gas, liquefied petroleum gas, ethanol and biodiesel. The use of alternative fuel and new energy vehicles should be given preference in urban public transport, sanitation, postal and logistics sectors.

The ministry said China's pollution control on motor vehicles should reach an internationally advanced level by 2020, with at least 95 percent of scrapped vehicles recycled.

The government unveiled a five-year national clean air action plan in 2013, aiming to improve air quality through measures such as closing factories, limiting cars and replacing coal with clean energy.