Days of torrential rain, flash floods and landslides across southern China have forced authorities to enact emergency plans, as swollen rivers threaten to overflow further, potentially disrupting the lives of millions.

On Thursday, Guangdong upgraded an emergency response plan for disasters like landslides and flooding to the second-highest level, helping to coordinate and deploy resources across the province.

Several other provinces have already activated a Level-IV emergency response for flood control as this year's flooding season kicked into high gear.

China's flood control emergency response system has four levels, with Level-I being the most severe.

Heavy rain and landslides in the coastal provinces of Guangdong and Fujian have already killed at least nine people and left several people missing.

Authorities in Guilin, a major city in Guangxi in southwest China, raised a "red" flood warning signal, the highest level, late on Wednesday when the water level of the Li River, which runs through the city, reached 3.61 metres above the warning line, China Daily reported on Thursday.

The water level at the river's hydrological station in Rongjiang township hit a record high, threatening residents' lives and properties along the river, the report said.

Guilin authorities urged departments, townships and scenic spots to help prevent and combat possible flooding in the coming days as water levels at major rivers continue to rise, according to state media.

Moderate to heavy rain is expected to start again from Friday through Monday in the middle and lower reaches of the Yangtze River, the longest waterway in Asia, according to China's Central Meteorological Observatory. (Reuters)