Military assault boats are being used to ferry emergency food and water supplies to 50,000 people trapped by flood waters for five days in a city in south China's Hainan Province.

Seven tonnes of flour was used daily since Saturday to make steamed buns, which were being sent to residents of worst-hit Wenchang City, said local officials.

Rescuers have also been ferrying in bottled water, instant noodles and rice for the last five days, said a spokesman with the municipal Civil Affairs Bureau.

More than 20,000 people living in ground-floor residences have been relocated, since the city's Chizhi Reservoir breached its dikes Friday morning.

Waters as deep as four meters had submerged many parts of the city and cut water and power supplies. In hard-hit Wencheng Township, the road link to the outside has been cut.

Vegetable prices in Hainan have jumped by about 30 percent as local crops have been destroyed and cities like the provincial capital Haikou are relying predominantly on vegetables shipped in from outside.

Xinhua agricultural produce prices monitoring system detected price surges in many vegetables, with the biggest jump of 33 percent in the price of Chinese cabbage from Friday.

A total of 230,000 people had been displaced in Hainan, better known as a tropical beach resort, as of Saturday due to the torrential rain, which has affected more than 1.64 million people, a fifth of the provincial population, said a spokesman with the provincial disaster control headquarters.

Heavy rains began pounding Hainan on Sept. 30, leaving at least one person dead and three people missing.