Xiaolangdi reservoir dam in Luoyang in China's central Henan province Photograph:( AFP )
President Xi Jinping described the situation as "extremely severe" with flood control measures entering a "critical stage", state media reported
The military blasted open a dam to release floodwaters threatening one of its most heavily populated provinces, as at least 25 died in torrential rains in central China.
Those who died include a dozen passengers trapped in a flooded subway.
The dam was blasted late Tuesday night in the city of Luoyang, just as severe flooding overwhelmed the Henan provincial capital of Zhengzhou, trapping residents in the subway system and stranding them at schools, apartments and offices.
President Xi Jinping described the situation as "extremely severe" with flood control measures entering a "critical stage", state media reported.
Approximately 200,000 residents were evacuated in Zhengzhou, local government officials said.
The rainfall in the region was the heaviest since record-keeping began 60 years ago as scientists say climate change is worsening flooding around the world.
At least four were killed in nearby Gongyi city where houses and walls have collapsed.
Li Rongguang, a woman in her sixties, told AFP she came to Zhengzhou to see a doctor but was stranded when trains were halted due to the storm.
"I want to get home as soon as possible," she told AFP, sitting by the side of the road. "I can't take this anymore."
Authorities have issued the highest warning level for Henan province as floods continue to hammer the region.
The statement said "key protected cultural relics suffered varying degrees of water damage," but said they were now safe, without providing precise details.
Thousands of soldiers have been deployed to other rivers nearby to reinforce embankments with sandbags
"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."
Watch | Gravitas: China Floods: Heaviest rain in 1,000 years leads to devastation