Dikes of the Shenjiakeng Reservoir, a rainwater pooling dam in the eastern Zhejiang Province's Zhoushan city, collapsed this morning flooding the nearby areas.
Five people were killed and three others were reported missing, state-run news agency Xinhua reported.
A water conservancy expert team was rushed to the site to help carry out emergency repairs of the dam.
Zhejiang has been lashed by downpours over the last few days with the arrival of typhoon Haikui, which hit the province on Wednesday morning before moving into neighbouring Anhui Province.