BEIJING, Nov. 15 (Xinhua) -- Beijing has completed its plan to make 450 more villages go coal-free this year, just in time for the start of the winter heating season, according to the Beijing Municipal Commission of Rural Affairs.

Beijing stepped up efforts to make villages coal-free as coal burning in the winter heating season put pressure on the city's commitments to smog-free days.

The metropolis of over 21 million people launched a program to wean off coal use in favor of clean energy in 2013, in its drive to improve air quality.

As of late October this year, nearly 3,000 villages in the city had gone coal-free, with around 858,100 households switching to clean energy for winter heating.

Air quality in Beijing has since improved over the years. The city's average density of PM2.5, an air pollution indicator, was 55 micrograms per cubic meter during the first seven months of this year, down 14.1 percent from the same period last year.

In 2017, the number was 58 micrograms per cubic meter in the city, 20.5 percent less than in 2016.

Chinese Vice Premier Han Zheng last month stressed the use of clean energy for winter heating in the country's northern region. China should ensure that people in the north are kept warm and safe during winter while also making progress in improving air quality, Han said.

According to an official plan released in September, a total of 3.62 million additional households in Beijing, Tianjin and 26 other cities in nearby regions were expected to have had their coal-fired heating systems converted to clean energy by the end of October 2018.