BEIJING, June 4 (Xinhua) -- Automobile emissions have become a major source of air pollution in China and it's increasingly urgent to take measures, according to a recent report.

China remained the world's largest automobile market last year, with about 310 million vehicles, up 5.1 percent year on year, according to the report released by the Ministry of Ecology and Environment (MEE).

Some cities saw increasing air pollution due to a combination of coal burning and vehicle exhaust emissions. Studies of the course of pollution in Beijing, Tianjin, Shanghai and another 12 Chinese cities found that vehicle exhaust emissions contributed from 13.5 percent to 52.1 percent of major pollutants.

The MEE will speed up drafting an action plan to deal with diesel-powered trucks, which are considered to be a major air polluter, it said in a statement.

The ministry will develop the strictest environmental regulation mechanism for vehicle exhaust emissions and promote clean diesel-powered vehicles and green transportation, the statement added.