Torrential rains triggered landslides and flooded a city in central China, killing at least 25 people. Images showing passengers struggling against chest-high water inside a train carriage have surfaced. President Xi Jinping described the situation as "extremely severe" with flood control measures entering a "critical stage".

The rain has forced the local government to evacuate residents to safety. Here is what we know so far:

ALSO READ | Is global warming behind the floods in Germany?

Around 200,000 city residents were evacuated in Zhengzhou -- a city of over 10 million people.

The rainfall in the region was the heaviest in 60 years, with Zhengzhou seeing the equivalent of a year's average rainfall in just three days.

Rainstorms submerged Zhengzhou's metro late Tuesday, killing 12 people and injuring five, while city officials said hundreds were rescued from the subway.

Passengers of a train were rescued by cutting open the roof of the coach to pull people to safety, local media reported. 

ALSO READ | Why have the floods in Europe been so deadly?

Four were killed in the nearby Gongyi city where houses and walls have collapsed, the official Xinhua news agency said.

Authorities have issued the highest warning level for Henan province as floods continue to hammer the region.

As the scale of the disaster continued to wreak havoc, the Chinese army said it had averted the collapse of the stricken Yihetan dam around an hour from Zhengzhou city.

ALSO READ | What caused flooding in Germany?

The People's Liberation Army said blasting operations had been carried out at the dam and troops had "successfully opened a new flood diversion opening".

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

"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," he added.

Over 6,000 firefighters, and nearly 2,000 members of the police and Chinese military, are involved in search and rescue operations across disaster hit areas.