SEOUL, Nov 1 (Reuters) - South Korea’s six older coal-fired power plants will be retired by 2021, a year earlier than previously planned, as part of the country’s ongoing efforts to curb air pollution, the prime minister’s office said on Friday.

South Korea, Asia’s fourth-largest economy, runs some 60 coal-fired power plants, generating around 40% of the country’s electricity, but coal has been blamed for worsening air quality in the country.

The six older coal-fired power plants account for 7% of the total installed coal power capacity, or 2.6 gigawatts, according to Reuters calculations based on data from Korea Electric Power Corp.

South Korea stops operations at some ageing coal-fired power plants from March to June every year to reduce air pollution levels and put a cap on coal power operations when an air pollution advisory is issued.

Meanwhile, the prime minister’s office said the government will decide in late November the number of coal power plants to be shut down between December and March to further lower the country’s air pollution levels.

In September, South Korea’s presidential committee recommended halting up to 14 coal power plants between December and February and up to 27 in March, ramping up the country’s anti-pollution measures. (Reporting By Jane Chung; Editing by Shounak Dasgupta)