Rescuers watch as water is pumped from a road tunnel filled with vehicles caught in floodwaters in Zhengzhou. AP

Rescuers used bulldozers and rubber boats to move residents out of flooded neighbourhoods in central China on Saturday.

The death toll from catastrophic flooding in the central Chinese city of Zhengzhou has risen to 56, state media reported on Friday.

The rains that started on Tuesday in densely populated Henan were the heaviest on record, according to the government.

A woman carrying a child and belongings wades through floodwaters following heavy rainfall in Zhengzhou. Reuters

On Saturday, skies were mostly clear but parts of Zhengzhou and other cities including Xinxiang, Hebi and Anyang still were under water.

The official China Daily newspaper and other media said the number included just Zhengzhou, the capital of Henan province. Other areas of the province have also faced heavy downpours, and rivers and reservoirs burst their banks.

The reports said losses in Zhengzhou totaled about $10 billion as the city continues to drain inundated areas, remove mud and cart away damaged vehicles and household items.

In earlier reports, the downpour caused landslides and flooded large areas of Henan province, including its capital Zhengzhou.

Twelve people died and five were hurt after the rains flooded underground metro stations. Hundreds were removed from other underground tunnels.

READ MORE

At least 125 killed in India heavy monsoon rains

Heaviest rain in a thousand years batters China; 200,000 evacuated

A dozen cities in the country have been badly flooded.

A year’s rainfall buffeted the city, which has 10 million inhabitants, in just three days.

People walk through floodwaters along a street in Zhengzhou in central China's Henan Province, on Tuesday. AP

Horrifying images that went viral on social media platforms showed shocked passengers battling to keep their heads above the fast-rising waters inside a train coach. Rescuers had to prise open the roof of the bogey to pull the passengers to a safe area.

Four were killed as houses collapsed in nearby Gongyi city.

A man carrying a woman wades through a flooded road following heavy rainfall in Zhengzhou on Tuesday. Reuters

President Xi Jinping described the situation as "extremely severe" with flood control measures entering a "critical stage", state media reported on Wednesday.

"Some reservoirs had their dams burst... causing serious injury, loss of life and property damage," Xi Jinping said, according to state broadcaster CCTV.

"We have already entered the critical stage of flood control, leaders and cadres from all walks of life must... take the lead in commanding, quickly organise forces for flood protection and disaster rescue."

Relatives outside Zhengzhou made anxious pleas on China's Weibo for information as communications to the city went down.

"Is the second floor in danger? My parents live there, but I can't get through to them on the phone," one user wrote.

"I don't know more about their situation. I'm in Tianjin and my parents are in Zhengzhou," she said, giving her surname only as Hou when contacted by AFP.

"I'm very anxious."