Urumqi, one of China's most polluted cities, plans to move dozens of factories from urban areas and tear down thousands of coal-burning boilers this year to clean its skies of their habitual winter smoke.

The government of the northwest China city, capital of Xinjiang Uygur Autonomous Region, aims to cut 5,000 tons of sulfur dioxide emissions this year, more than double the estimated 2,000 tons of emissions cut in 2010, said a spokesman for the municipal environment department Monday.

Urumqi's severe air pollution is mainly caused by industrial activities and winter heating supply. The city emitted 128,000 tonnes of sulfur dioxide and 61,000 tonnes of soot in 2009.

Residents complain that air pollution in Urumqi has grown so serious that the city seems to be constantly shrouded in thick black smoke during the winter.

Urumqi Mayor Jerla Isamudinhe said at the annual meeting of the city's legislature, which ended over the weekend, that the government would push to change the city's winter heating sources.

About 5,000 coal-burning small boilers used for winter heating will be dismantled in favor of collective combined power and heat generation facilities, and the use of natural gas, the spokesman said.

The cost of building the combined power and heat generation plants was estimated at 4 billion yuan, said the spokesman.

In addition, 47 polluting factories would be moved from urban areas while 20 would be upgraded to reduce sulfur dioxide emissions, he said.