At least 20 people have died in the past week as torrential rain batters swathes of China, with at least six killed by lightning, thousands of homes destroyed and more than 300,000 evacuated, state media said.

There had been six deaths from lightning strikes in the central province of Jiangxi since last Friday, the official Xinhua news agency reported.

There were other fatalities from lightning in Guizhou in the southwest, it said, where a total of seven people died.

A landslide in the province early Thursday buried eight people, Xinhua said, with two rescued by mid-morning but six still missing.

Officials in Guizhou are bracing for more devastation, the China Daily said, reporting a warning that "local authorities should make full-scale preparations for geological disasters that could be triggered by rains".

The most severe downpours, which began on Sunday night, destroyed 5,800 homes and damaged another 16,300 in Guizhou, Xinhua said, in a report late Wednesday.

Three people were reported missing and more than 91,000 relocated in the province, the report added.

Five people were killed and 14 missing in landslides in Anhua county in Hunan, also in central China. Across the province the torrential rain has destroyed 1,330 homes and forced 283,000 people to be relocated.

Flights out of the rain-hit area have been delayed while incoming aircraft have been diverted elsewhere, Xinhua said, with at least 4,000 people stranded at Longdongbao airport in Guizhou's provincial capital Guiyang.