Torrential downpours, mudslides and floods hit the provinces of Hunan, Guangdong, Guangxi, Guizhou, Jiangxi and Fujian since the weekend, prompting evacuation of 788,000 people, the Civil Affairs Ministry said.
Livestock were left to drown as people fled their homes, power lines were toppled and roads made unpassable.
By Tuesday, flooding and mudslides had caused direct economic damage of about 4.7 billion yuan ($615 million), with 69,000 homes and 1,360 square km (525 square miles) of crops destroyed, the ministry said.
In the worst hit area of northeastern Guangdong, paramilitary troops and other rescuers used speedboats to deliver urgent supplies to 24 villages in Huangjin township which had been submerged by mountain torrents and the overflowing Hanjiang River, a local official said.
"We are distributing instant noodles, rice and medicine," the official, surnamed Liu, told Reuters by telephone.
It was only drizzling on Wednesday but a dozen villages were still under water and roads were cut, he said. Rescuers were disinfecting areas where water had retreated to avert epidemic.
Authorities in Meizhou municipality, which includes Huangjin, were rushing to repair dykes along the Hanjiang ahead of heavy rains forecast for the rest of the week, Xinhua news agency said.
Floodwaters had reached the second floors of homes in Huangjin last Friday, forcing many to flee leaving valuables, poultry and livestock to be destroyed, Liu said.
An 8-year-old boy died and a man in his 50s went missing in the floods in Huangjin, he said.
More than 3,000 people were living in tents in the township of 37,000 and many others were sheltering with relatives whose houses on higher ground had survived the flood, he said.
"We will not be able to think about restarting life until people get stabilised in their minds," said Liu. "The losses were too huge."
Rice crops, only about a month from harvest, were destroyed across Meizhou, an underdeveloped hilly area known for its unique Hakka culture.
Some 260 mm of rain in seven hours on Tuesday night flooded streets in Liuzhou city in the southwestern region of Guangxi, submerging more than 20 big basement garages, Xinhua said.
Heavy rain would continue to batter at least seven provinces across south China on Wednesday, the National Meteorological Centre said on its Web site (www.nmc.gov.cn), compounding floods which have "affected" 13.6 million people.
For the first time this year, the Three Gorges Dam on the mighty Yangtze River, the world's biggest hydropower project, discharged water on Tuesday to lower the level in the reservoir after excessive rainfall upstream, Xinhua said.
When the level rose to 144.9 metres, two spillways were opened to maintain it at 144 metres.
- Reuters - Thomson Reuters Foundation
- For more humanitarian news and analysis, please visit https://www.trust.org/alertnet