Heavy flooding in Henan province in central China resulting from torrential rain since last Saturday has killed 25 people and displaced hundreds of thousands.
Chinese President Xi Jinping yesterday called for an all-out effort to help those affected, urging the authorities to prioritise residents' safety and property.
The meteorological bureaus for Henan and provincial capital city Zhengzhou have raised the emergency response to Level 1, the highest level.
The People's Liberation Army and Ministry of Emergency Management dispatched about 5,000 soldiers and firefighters to help with rescue work.
Videos on social media platforms Twitter and Weibo showed commuters in Zhengzhou stuck in an underground train carriage, at least waist-deep in murky water. Twelve people died and five others were injured in the incident.
One of the 500 people rescued, who uses the handle Qijiqiyuan on Weibo, recalled the ordeal that lasted for hours.
"The water kept rising... At first, the level was at our knees, then our waist... I started panicking when the water rose to my chest," she wrote in her post.
She described how it appeared as if everyone would run out of air soon. "I heard a woman giving her family members her bank information in case she couldn't make it. I called my mum and told her that I might not be able to make it."
Qijiqiyuan said she was about to faint when rescuers broke open the windows of the train carriage.
"This was my closest encounter with death," she said. "I would have so many regrets if I had died. I would have regretted not meeting so many people and not eating my favourite spicy hotpot. Most of all, I would've regretted not saying 'I love you' to my parents, grandmother and younger brother."
On the streets, cars and motorcycles could be seen floating, while some residents were clinging to trees to keep their heads above the gushing water.
Flights and inter-city trains stopped running.
In Zhengzhou, more than 200mm of rain fell in one hour on Tuesday, meteorological data showed. The amount of rainfall between last Saturday and Tuesday in the city reached 617.1mm, nearing the annual average of 640.8mm.
More than 30 reservoirs in the province have exceeded their warning levels.
Henan, where the famous Shaolin temple is located, is one of the most densely populated provinces in China, with 94 million residents.
Posts with the hashtag "Torrential rains in Henan" have been read 3.4 billion times on Weibo and spurred 6.5 million discussions as at 6.30pm on Tuesday, with users in Henan complaining of power and water supply being cut. Food supplies were also reported to have been affected.
Earlier this month, China's National Climate Centre warned of more extreme weather events than usual, and predicted poor weather conditions for the rest of the summer. It estimated rainfall to be 20 per cent to 50 per cent more than usual, and said that some major rivers were likely to swell and cause floods.
The Yellow River, the second-longest river in China after the Yangtze, runs through nine provinces, including Henan.
Meteorologists in China blamed Typhoon Yanhua for the unusual rainfall in Henan.
They said that Yanhua, or In Fa, has been approaching Fujian province in south-eastern China, forcing water vapour to be pushed from the sea to Henan.
The air flows converged and travelled upwards when they hit the mountains in Henan, causing rainfall to be concentrated in the region. The downpour is expected to ease on Monday.
Citing preliminary studies, weather and climate scientist Koh Tieh Yong at the Singapore University of Social Sciences said that heavy rainfall has occurred in central China more frequently in recent decades because global warming has expanded the subtropical zone in the East Asia-West Pacific region northwards.
"The prolonged and intense rainfall in Henan province this year, when taken together with other heavy rainfall events in the recent decade or two, may be a manifestation of such a northward shift in the summer monsoon rain belt," he said.