Heavy rainfall inundated streets and caused major rivers to burst their banks in the central province of Henan on Tuesday.
The People's Liberation Army (PLA) also reported that the storm had damaged the Yihetan dam near the city of Luoyang. They warned that "the dam might collapse at any time" after a 20 meter breach had appeared in the structure.
At least 25 people dead, officials say
Officials in the provincial capital of Zhengzhou say at least 25 people have died with concerns more bodies will be found. The Chinese central government upgraded its flood emergency response from level III to level II on Wednesday due to the crisis.
Local authorities in Henan said thousands of people have been evacuated from the city as a result of the floods.
"As of 7 a.m. on July 21, almost 200,000 people were evacuated in an emergency and 36,000 city residents were affected by the disaster," Zhengzhou city officials said in a statement.
Soldiers have been leading rescue efforts there.
Unusually heavy rain has been falling in the province — twice the size of Austria and with a population of 94 million — since the weekend.
Dozens of cities have seen massive disruption to transport services. Zhengzhou, which is situated on the Yellow River, had to stop all subway services on Tuesday after 200 millimeters of rain fell in just one hour.
The Guajiaju Dam near Zhengzhou has reportedly collapsed, according to state news agency CGTN.
A video shared widely over social media showed torrents of water cascading through one of the city's subway stations as well as people standing waist-deep in water inside a subway train.
Devastating flooding around the world
Some 10,000 residents in the province had been relocated to shelters, according to Xinhua News Agency.
Thousands of PLA soldiers, police officers and militia members have been dispatched to assist in rescue operations in Henan, the state-run People's Daily outlet reported.
Chinese President Xi Jinping addressed the flooding situation in Henan on Wednesday in a statement.
"Some rivers have exceeded monitoring levels, some dams have broken down, while some railway services have stopped and flights cancelled, causing heavy casualties and property losses," the Chinese leader said on state television. "Flood prevention efforts have become very difficult."
Henan is a particularly populous province and a major transport hub. It is also a key base for industry and agriculture.
Summer often brings heavy rain and flooding to the region, but growing cities and changes to land use have increased the costs of flood damage.
The flooding in central China comes days after catastrophic flooding led to the deaths of over 160 people in western Germany.
New York City was also left with flooded subway stations after being hit by tropical storm Elsa earlier in the month.
Fears over key cultural sites
The heavy rain has sparked concern for the Longmen Grottoes — a UNESCO World Heritage site featuring thousand-year-old Buddhist carvings in limestone cliffs.
The world-famous Shaolin Temple in Dengfeng, known for its monks' mastery of martial arts, was also forced to shut.
Since Saturday, over 3,500 weather stations have recorded rainfall over 50 mm. Some 150 stations saw rainfall exceed 250 mm.
The highest amount recorded by the provincial weather bureau in that period was 498 mm of rain in the city of Lushan.
