China's five main power generators recorded losses in their thermal power business last month, despite an increase in wholesale power tariffs, the China Electricity Council said Tuesday.

China Huaneng Group, China Datang Corp., China Huadian Group, China Guodian Corp. and China Power Investment Corp. lost CNY1.69 billion ($261 million) on thermal power generation in May, steady with April's losses, due to high coal costs, the association said on its website.

The five state-owned companies recorded CNY12.2 billion of losses from January to May, it said.

China raised on-grid power tariffs--paid by China's two grid operators to generators for their output--in 12 provinces by an average of CNY0.02/kWh, around a 5% hike, as of April 10, and in three more provinces from June 1.