Death toll rising
Casualties from the storms rose throughout Thursday, as officials worked to tally the total number of dead and injured, as well as the number of homes damaged.
"Tornadoes never happened here in the past - this is the first time"
Liu Fang, a Liangping district official
Local papers reported that at least 1,000 homes were destroyed and 10,000 damaged.
"Tornadoes never happened here in the past - this is the first time," Liu Fang, a local township official in Liangping county, one of the hardest-hit areas, told the AFP news agency.
"So far, six have died and 38 are injured in our township. The electricity has been cut, and some houses were damaged due to the strong wind."
The injured were being taken to local hospitals while tents were being set up for those whose homes were destroyed, Li said.
Up to 157 millimetres of rain had fallen in parts of the region - stricken by a severe drought since last year - from late Wednesday to Thursday afternoon, Xinhua said.
The storms were caused by a heat wave from the south colliding with a northern cold front, the report said, citing meteorologists.
An official in Xinmin township told AFP that older houses suffered "very serious" damage including collapses, although newly built brick homes were also damaged.
"We're still gathering information about the disaster," the official said.
According to the People's Daily, the ruling Communist Party's newspaper, as many as 1,000 homes in six towns had at least partially collapsed in the storm, while thousands of others were damaged.
Power was cut in several areas, many roads in the region were blocked by flooding, and bridges also suffered damage, the report said.
The cost of the damage in the six towns was expected to surpass $3 million, it added, citing preliminary estimates.
Chongqing, a province-sized municipality, has a population of more than 30 million people.