Huge algae outbreaks again pose a threat to drinking water supply from Taihu and Chaohu, two of China's major freshwater lakes.

Satellite pictures showed blue-green algae covering about a third of both lakes in the country's densely populated east, according to the National Satellite Meteorological Center.

In the 2,400-sq-km Taihu Lake, the country's third largest freshwater lake on the border of Jiangsu and Zhejiang provinces, about 800 sq km is covered with the fast-growing and foul-smelling green plant.