In addition, 250,000 people in Dazhou, Sichuan province, had been made homeless and forced to relocate with a total of two million people affected, the official from the city's civil affairs department said.
The water level has reached up to the third floor of some buildings, submerging the streets in the city, the Xinhua news agency reported earlier.
Newspapers Sunday carried pictures of rescuers plying the deep floodwaters in inflatable boats. A baby was shown in one photo being transported by police in a floating plastic tub.
All roads leading to the city had been cut off following torrential downpours which have dumped 461 millimetres (18 inches) of rain on the city since Wednesday, reports said.
Police were evacuating residents to safe areas and government officials had rushed to the flood-hit zone, Xinhua said.
State media Sunday reported a different death toll from the one the local civil affairs department gave.
The Sichuan Daily said 20 people have died in Dazhou, with five missing. They were among 65 people who died and 30 missing due to flooding in Sichuan from June 28 to July 8, the daily said.
The official China Central Television Station, meanwhile, said 37 people have died and seven are missing from "recent" flooding in Dazhou as well as six other cities in Sichuan. It did not specify the timing of the floods or give a breakdown of the deaths by city.
The report said 420,000 people from the seven cities have been relocated, among 7.2 million people affected.
China's civil affairs and finance ministries alloted 23 million yuanmillion US dollars) in disaster relief funds to the cities, it said.
The latest deaths bring the toll from flooding this year in China to about 800 people killed or missing, with the main July-August flood season just starting.
Floods have always been part of life in China but this year they have been more devastating than usual.
The most severely affected areas have been the southern provinces of Zhejiang, Fujian, Jiangxi, Hunan and Guangdong, as well as Guangxi Zhuang region, where unusually heavy rain had caused rivers to swell.