The Shichahai area is unique in Beijing because it is an open tourism area, where chengguan work with tourism management officers to maintain order.

Further investigation will focus on who started the fight and those responsible will be punished, Sun said.

The case triggered heated discussion online about the behavior of government officers as well as of Tian's project.

He wrote on his micro blog that he had learned that selling goods on the street might violate city regulations but the project aimed to let his daughter experience society, which he thought was a different case.

"I did not expect that government officers would beat me so severely in such a famous scenic spot in Beijing," Tian wrote on Sunday in a post.

Tian, the deputy head of a magazine in Beijing, asked the chengguan to release related recorded footage of the incident to give the public a complete picture.

Mo Yuchuan, a law professor at Renmin University of China, said that although some street vendors conduct illegal business operations, chengguan and other government officers should persuade them to stop rather than react to them with violence.