The death toll from a mudslide triggered by heavy rain on the outskirts of the western Chinese city of Xi’an has risen to 21 and rescuers were still looking for six missing people, authorities said.

"Twenty-one people were found dead so far, and six others are still missing," the Xi'an emergency management bureau said in an online statement on Sunday. State media had earlier put the toll at four.

The mudslide and a flash flood on Friday evening also damaged a highway and knocked out power to 900 households, the Xi’an Emergency Management Bureau said on its social media account.

It said rescue teams totalling 980 people with dogs were looking for the remaining missing people.

A hundred soldiers as well as firefighters were mobilised for the relief operations "which are continuing", according to CNR.

CNR broadcast images on Weibo showing rescuers clearing rocks and trees from the edge of a river and carrying victims on stretchers.

Unusually severe rains and flooding

Typhoon Khanun, which pounded parts Japan and South Korea, weakened into a tropical depression when it made landfall in China's northeastern Liaoning province on Friday night.

Rain still posed flooding risks to low-lying cities including Anshan, where 17,859 people had been evacuated, according to state-owned China Central Television (CCTV).

Overnight rainfall in Liaoning peaked at 52 mm (2 inches) per hour, with four reservoirs exceeding flood limits, CCTV said.

Khanun came as the country reels from the impact of Typhoon Doksuri, which lashed northern China with torrential rain and flooding after it made landfall on July 28.

China's State Flood Control and Drought Relief Headquarters and the Ministry of Emergency Management held a special meeting on Sunday morning to discuss flood prevention and emergency response measures in badly affected provinces such as Liaoning, Shaanxi, Tianjin and Chongqing, CCTV reported.

Parts of China suffer heavy rains and flooding every summer, but this year has been unusually severe in some areas, while other regions struggle with drought that is damaging crops. The government earlier reported 142 people were killed by flooding and landslides in July.