BEIJING, Aug 14 (Reuters) - The death toll from a mudslide in China's northwestern city of Xian has risen to 21, with six people still missing, the city's emergency management authority said on Sunday (Aug 13), as China grapples with unusually high summer rainfall.

State-owned China Central Television (CCTV) had earlier reported that Friday's mudslide in the city of Xian, which followed heavy rainfall in the region, left a total of 18 people dead or missing, with two confirmed casualties.

A video released by the official Xinhua news agency showed broken trees and rubble piling up along muddy roads in a village that lies in a mountainous area, with houses and infrastructure damaged or destroyed.

The mudslide destroyed two houses and cut power to 900 households, the authority said in a statement on its WeChat account.

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 CCTV.

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

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

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

Warmer temperatures have also fuelled powerful convective weather in many parts of China amid an unusually wet summer.

On Saturday morning, a dramatic supercell storm formed in China's northwestern region of Xinjiang. A video posted by state media People's Daily showed thick swirling clouds hanging low above the ground, darkening the sky.

"The force of nature is irresistible," one commentator exclaimed on the video.