Rain storms and floods have killed at least 23 people across southern China in recent days and made thousands homeless, Xinhua news agency said on Saturday.

"Millions of people are suffering," it said.

Storms killed seven people and left four missing in the southern province of Guizhou on Friday and Saturday. Nearly 20,000 hectares (77 sq miles) of cropland were flooded and 3,000 houses destroyed, Xinhua said.

In Guangdong province, bordering Hong Kong, heavy rain triggered landslides killing three people and destroying 788 houses and about 1,120 hectares of cropland, Xinhua said.

Storms cut off a railway link between Meizhou and Shantou in Guangdong leaving about 1,100 passengers stranded on Friday.

In neighboring Guangxi, two people were killed in torrential rain that destroyed 610 homes, Xinhua said, citing flood control authorities.

In Guangxi, high school students sitting all-important university entrance exams on Thursday and Friday had to be evacuated as heavy rain submerged their classrooms, Xinhua said.

Storms also broke 29 reservoirs, 362 embankments, 165 roads and forced 59 factories to suspend production, Xinhua quoted Chen Rundong, deputy head of the regional flood control office, as saying.

On Friday, Xinhua reported seven deaths and nine injuries on in the Liangshan region of Sichuan province from hailstorms, lightning strikes and landslides. Xinhua did not give details of all the deaths.

China's central Hunan province was on high alert after four successive days of rain swelled the Xiangjiang river to 4.6 meters above the "warning level" and to its highest mark in 20 years, Xinhua said.

"We have stepped up our guard against flooding as two more heavy rainstorms are forecast over the next four days," Xinhua quoted Xie Kangsheng, a Hunan government official, as saying.

Storms in Hunan had killed three people, left 158,000 homeless and cut off water supplies to 75,000, Xinhua said on Friday.

Late last month, lightning, mudslides and floods in Sichuan province killed 43 people, state media reported.

China's typhoon season is just getting under way in the south. Experts last month warned that China's Yangtze river could flood badly this year, for the first time since 1998, when floodwaters from the country's longest river killed more than 3,000 people.