The tornado swept through Lingbi county, Anhui province early Saturday, flattening a factory and killing eight people on the spot, according to an earlier Xinhua news agency report.

Seven more people later died.

The China Youth Daily reported among the dead 11 were secondary school pupils attending summer holiday classes.

Another 30 were hurt, it said.

"The death toll hasn't changed," an official surnamed Hu at the Suzhou city production and relief bureau told AFP, adding 37 were seriously injured.

State television footage showed collapsed houses and overturned vehicles in the aftermath of the tornado that lasted some 20 minutes.

Rescue efforts were ongoing, the report said.