JIIANLI COUNTY, CHINA/SHANGHAI - Survivors of a ship which capsized on China's Yangtze River in a storm late on Monday have recounted how quickly the tragedy occurred.

Tour guide Zhang Hui, 43, told Xinhua the capsize happened very fast and he scrambled out a window in torrential rain clutching a life vest as he could not swim.

"Wave after wave crashed over me; I swallowed a lot of water," a Reuters report citing Xinhua quoted him as saying.

Xinhua said he survived after floating in darkness for 10 hours. He was unable to flag down passing ships and finally struggled ashore as dawn broke holding onto a branch.

Meanwhile, the Yangtze River navigation administration also cited the ship's captain and the chief engineer as saying that the ship sank quickly after it was caught in what was described as a tornado.

The pair were among the few to be rescued and have since been detained by police for questioning, Xinhua said.

According to Xinhua, initial investigations had found the ship was not overloaded and it had enough life vests on board for its passengers. Those rescued were wearing life vests, Xinhua said.

State radio said the ship went over in about two minutes and no distress call had been issued. Seven people swam to shore to raise the alarm, media said.

Rescuers were on Tuesday fighting bad weather as they searched for more than 400 people, many of them elderly Chinese tourists, still missing in what was likely China's worst shipping mishap in almost 70 years, Reuters reported.

Divers and other rescue workers desperately tried to reach five people they found trapped in the upturned hull of the Eastern Star, a fraction of the 458 people state media reported were on board when the ship capsized in a storm late on Monday.

About another dozen people had been rescued and five bodies recovered, media reported, leaving more than 430 people unaccounted for.

The People's Daily, which published a passenger manifest on its microblog, said those on board the Eastern Star ranged in age from three to more than 80.

Among those on board were 406 tourists, aged from about 50 to 80, on a tour organised by a Shanghai tour group, along with 47 crew members and five tour guides, the People's Daily said.