Torrents of mud and water began hitting mountainous areas of Gansu province on Thursday, with the death toll listed as 10 on Friday as rescuers searched for at least 33 missing people.

Natural disasters are common across China, particularly in the summer, when some regions experience heavy rain while others bake in searing heat.

Chinese President Xi Jinping called for the "utmost effort" in rescuing missing people, state broadcaster CCTV reported on Friday.

The death toll stood at 13, with the number of missing now listed as 30, state news agency Xinhua said on Saturday.

Hundreds of people had been rescued and thousands more evacuated, Xinhua added.

It quoted a rescue official describing the situation as "complex" due to the mud and rough roads, with telephone lines and electricity also cut.

State media on Friday put the number of people trapped in the mountainous Xinglong area at 4,000, with heavy rain pushing garbage into roads.

Beijing's top economic planner has allocated 100 million yuan ($14 million) towards disaster relief in Gansu.

Authorities also announced a yellow alert on Saturday for torrential rains and activated a flood response plan in the provinces of Jiangsu, Anhui, Hubei and Chongqing, CCTV said.

China's south has also experienced torrential downpours this week, with tens of thousands of people evacuated across Guangdong.

Heavy rain in Beijing in the north also killed 44 people last month, with the capital's rural suburbs hardest hit and another eight people killed in a landslide in nearby Hebei province.

Scientists warn the intensity and frequency of extreme weather events will increase as the planet continues to heat up because of fossil fuel emissions.

China is the world's biggest emitter of greenhouse gases but is also a global renewable energy powerhouse.