China will ramp up its efforts to curb transportation pollution in the next phase of its campaign to improve air quality, an environment official said on Wednesday.

Liu Bingjiang, director of the Ministry of Ecology and Environment's atmospheric environment division, told a panel of international reporters in Beijing that an upcoming action plan on reducing air pollutants will focus on transportation-induced pollution, with a big leap in related work.

"Oxynitrides are now a major airborne hazard," he said at the event organized by the China Public Diplomacy Association.

Such pollutants are mainly generated by the consumption of fossil fuels, particularly by passenger cars, heavy trucks and cargo ships, he added.

Liu said the action plan, which is still being vetted by central authorities, marks the third phase in China's battle against air pollution.

China issued a five-year action plan in 2013 in response to heavy smog smothering many regions. It followed up with a three-year campaign to protect blue skies and further lower the concentration of PM2.5, particulate matter with a diameter of 2.5 micrometers or less, which can invade small airways.

The country's clean air campaign has coincided with the rapid progress of the electric car sector, and an increase in the number of large electric trucks used in sectors such as mining and construction.

Liu, also a standing committee member of the China National Democratic Construction Association and a political adviser, said more electric heavy-duty freight vehicles, coupled with replacing gasoline-powered buses with electric ones and limiting the number diesel vehicles in urban areas, have helped cleared reduce pollution.