Rescue workers swam through flooded buildings and used inflatable boats to pull people from roof and treetops in China, as authorities warned of a fresh wave of heavy rain bearing down on already waterlogged provinces.At least 24 people have been killed since torrential rains began sweeping southern and central China, up from 12 reported on Tuesday. Several others remain missing across Hubei, Hunan, and Guizhou provinces.In the central province of Hubei, emergency and military personnel were seen wading through chest-high water inside homes to reach residents, many of them elderly, footage from state broadcaster CCTV showed.In one scene broadcast by CCTV, rescuers struggled for an hour to free a man trapped behind a door by floodwater. In Dachong, a town in southern Guangdong, a man who had climbed a tree to escape rising water was pulled to safety in an inflatable boat, videos on the Chinese platform Douyin showed.In one of the hardest-hit areas, Baishuihe village in Enshi prefecture, roads were destroyed and communication facilities severely damaged, cutting the village off entirely. Ran Junjie, deputy head of Xuan'en county, told CCTV that following intensive rescue efforts, all stranded residents had been safely evacuated and relocated to local hotels or the homes of relatives.In Shimen county in Hunan, five people died, and 11 others remain missing after the first round of heavy rain that began on Sunday. The rainfall affected 23 townships across the county, with 103,247 residents impacted, local emergency authorities said. Three people were also killed in Majiang county in Guizhou after precipitation in some townships reached historic highs, while four more died in the province's Guiding county, where five others remained missing as of Tuesday afternoon.A police officer (L) helps a woman crossing a flooded road in Duyun, in China's southwestern Guizhou province (AFP/Getty)The death toll includes at least eight people killed after a pickup truck carrying 15 farm workers fell into a flooded river in the southwestern region of Guangxi, state broadcaster CCTV reported. Three others were killed by flash floods in a low-lying village in Hubei, and one person died in southern Hunan.Aerial footage showed floods swamping vast areas across Hubei and its southern neighbour Hunan. The rainfall system spans more than 1,000 kilometres, caused by the convergence of moisture from the Bay of Bengal, the South China Sea and the Pacific Ocean. Its slow-moving nature has led to exceptionally high cumulative rainfall, Chinese meteorologists said. In Hubei alone, 337 townships recorded more than 100mm of rain within a 48-hour window, shattering multiple local historical records.An aerial view shows a flood affected area after heavy rains in Duyun, in China's southwestern Guizhou province (AFP/Getty)China's weather bureau warned on Wednesday that a new round of rainfall would arrive on Thursday, bringing heavy precipitation across Shaanxi, Sichuan, Hunan, Guangxi and Guangdong. Authorities said areas faced high risks of landslides, flash floods and severe urban flooding. Schools, businesses and transport services have been suspended in parts of Hubei and Hunan, with authorities relocating residents in the most affected areas.China's National Development and Reform Commission said it had urgently allocated 50 million yuan (£5.5m) from the central government's budget to support post-flood recovery efforts in Hunan.In Hong Kong, emergency crews worked through the night using robots known as "water-pumping dragons" to clear widespread flooding in the northern New Territories after the city's first red rainstorm warning of the year was issued at 2.40am on Thursday, the South China Morning Post reported. The Drainage Services Department said it dispatched more than 60 emergency response teams, recording seven flooding cases across the New Territories by 5am. More than 100mm of rain fell in parts of the city, with videos circulating on social media showing a double-decker bus ploughing through floodwater deep enough to surge onto its lower deck, and a woman stepping off the vehicle into deep floodwater in Fanling.The Hong Kong Observatory said conditions would ease on Friday as upper-air disturbances moved away from the coastal areas.Additional reporting by agencies.