More than 120 electric, and 3,000 natural gas buses will be in operation in Beijing at the end of this year, Zhong Huaqiang, chief engineer of Beijing Public Transport Holdings, said on Friday.

He said the company will gradually introduce more new energy and clean-energy buses.

According to the capital's five-year Clear Air Action Plan, unveiled in September, the number of new energy and clean-energy vehicles will reach 200,000 at the end of 2017.

However, to meet the target, the capital has to tackle many obstacles, said Li Kunsheng, director of the vehicles emission management division under the city's environmental protection bureau.

Li said that increasing the number of new energy and clean energy vehicles needs more gas and battery charging stations.

Building those stations needs the cooperation of different departments for planning, such as the land property management sector.

Currently the city has five battery charging stations and Li did not elaborate how many stations will be built in the future.

To change the energy structure for winter heating was another measure to improve the city's air quality.

According to the city's five-year Clear Air Action Plan, the concentration levels of PM2.5 particles will be cut by 25 percent by 2017 from the 2012 level.

In the coming winter heating season this year, two gas-based power plants will begin operations.

Next year, two more such power plants will be in operation to provide heating for residents across the city, reducing the use of coal.