China's heavily polluted capital, Beijing, plans to reduce air pollution levels by 15 percent by 2015 and 30 percent by 2020 through phasing out old cars, relocating factories and planting new forests, state media said on Thursday.

The level of air pollution in the capital varies, depending on winds. But a cocktail of smokestack emissions, vehicle exhaust, dust and aerosols have at times blanketed Beijing in a pungent, beige shroud for days on end over the past few months, and has even forced the cancellation of flights.