XI'AN -- The northwestern Chinese city of Xi'an has set a target to be coal-free by 2020 in a bid to tackle air pollution.

Xi'an, capital of Shaanxi province and home of the Terracotta Army, has rolled out a spate of tough measures for cleaner air in a three-year action plan, the city government said Thursday.

The plan orders to improve the energy mix by using more natural gas and relocating or closing energy-guzzling heavy industries.

Local authorities plan to eliminate all coal-fired boilers by October and ban household coal use by the end of 2019. The coal-fired power plants and winter heating systems will also be switched to natural gas.

The city also plans to relocate or shut down all coal chemical, petrochemical and coking companies to help greatly improve the air in the ancient Chinese capital.

Xi'an achieved progress in its anti-pollution campaign between 2013 and 2017. Last year, the concentration of PM2.5, health-damaging airborne particles smaller than 2.5 micrometers in diameter, fell 30.5 percent from the 2013 level.

Shaanxi and several other regions around Beijing, including Hebei, Henan and Shandong, are at the forefront of the country's fight against air pollution.

Local authorities have been taking harsh measures to fight against air pollution over the past few years as the public are becoming more worried about the health impact of smog.