At least 21 people died as heavy downpours struck central China's Hubei province, authorities said Friday, weeks after record floods wreaked havoc and killed hundreds in a neighbouring province.

China has been battered by unprecedented rains in recent months, extreme weather that experts say is increasingly common due to global warming.

In Hubei, torrential rains caused power cuts and landslides, destroying hundreds of homes and forcing the evacuation of nearly 6,000 people, the province's Emergency Management Bureau said, as reservoirs reach dangerous levels.

"Twenty-one people were killed and four others are missing as heavy rain lashed townships from Wednesday," state broadcaster Xinhua reported Friday.

Footage showed families wading in water that had risen to almost hip level and carrying essentials in plastic bags in Yicheng, which saw a record 480 millimetres (around 19 inches) of rain on Thursday. Rescuers carried people to safety on bulldozers.

"Yesterday the water levels rose to about two to three metres. My neighbour's house was completely destroyed," a resident from one of the worst affected areas in the city of Suizhou told local media.

"We haven't seen so much rain in 20 or 30 years."

Hundreds of firefighters and thousands of police and military have been dispatched to the worst affected areas, China's Ministry of Emergency Management said.

Around 100,000 people were evacuated in the southwestern province of Sichuan last weekend as heavy rains caused several landslides. 

More than 300 people were killed in central China's Henan province last month after record downpours dumped a year's worth of rain on a city in three days.

China's Meteorological Administration warned that heavy rainfall was likely to continue until next week, with regions along the Yangtze River, including Shanghai, vulnerable to flooding.

Thousands evacuate as heavy rain hits Japan
Tens of thousands of people were urged to evacuate on Friday as "unprecedented" levels of torrential rain hit western Japan, raising the risk of floods and landslides, the weather agency said.

The downpours are forecast to continue for several days over a large swathe of the country, from the northern Tohoku region to Kyushu in the south.

"There is a possibility that a grave disaster will occur" in the coming days, a Japan Meteorological Agency (JMA) official told an emergency news conference shown live on public broadcaster NHK.

In Unzen city in southern Nagasaki prefecture, two houses were hit by a landslide with one woman in her 50s feared dead, a local official told AFP.

The heaviest rain was in Hiroshima prefecture, where non-compulsory evacuation orders were issued to at least 69,500 people and the top flood alert announced.

In the city of Hiroshima, "we have issued a special heavy rain warning. This is a level of heavy rain that we have never experienced before", the JMA said in a statement.

The agency official also called the rain in some areas "unprecedented".

The land ministry warned that water levels are extremely high in three rivers -- two running through the Hiroshima region, and one in southern Kumamoto.

Scientists say climate change is intensifying the risk of heavy rain in Japan and elsewhere, because a warmer atmosphere holds more water.

Downpours last month caused a devastating landslide in the central resort town of Atami that killed at least 21 people.

And in 2018, more than 200 people died as floods inundated western Japan during the country's annual rainy season.

On Friday, the JMA said that in the 24 hours from 6am on Friday, 300 millimetres (12 inches) of rain is expected in the northern part of Kyushu, with 200 to 250 millimetres forecast in many other parts of the country.