BEIJING -- China's environmental watchdog has suspended environmental approval for refining and chemical projects by the country's two oil and gas giants due to their weak environmental protection performance.

The China National Petroleum Corporation (CNPC) failed to meet the reduction target for chemical oxygen demand emissions in the 2012 annual evaluation on reduction of major pollutants, the Ministry of Environmental Protection statement said Thursday.

The China Petroleum and Chemical Corporation (Sinopec) failed to reduce targeted emissions of nitric oxide, according to the statement.