At least 16 people were killed and 36 others remained missing after a flash flood hit a county in China's northwest Qinghai province, local authorities said on Thursday.

Heavy rainfall, starting 10:25 pm on Wednesday, lashed Datong Hui and Tu Autonomous County, triggering flash floods and mudslides and causing rivers to change courses, according to the county's publicity department.

A total of 6,245 residents in six villages have been affected by the natural calamity, the publicity department said.

The province immediately activated its Level II emergency response for disasters, state-run Xinhua news agency reported.

Level-II is the second-most severe response in a four-tier disaster control emergency response system in China.

Local authorities have dispatched more than 2,000 personnel from the armed police, public security, emergency, health and other departments, as well as more than 160 vehicles, for rescue and relief efforts, the report said.

China is currently faced with extreme weather conditions, with some regions hit by record heat waves and severe drought.