The H7N9 bird flu virus spread within a private poultry company, the government of Yuyang district, Yulin city said in a statement, adding that chickens started dying on May 25.
A three-kilometre-radius area has been closed for disinfection, and the area will be closed for 21 days starting yesterday, state-run Xinhua news agency reported.
All poultry within the area will be culled and all poultry trading sites have been closed, the statement said.
The company is located in Niujialiang Township.
According to the National Health and Family Planning Commission, in March, 96 H7N9 infections and 47 deaths were reported nationwide.
In April, 81 infections and 24 deaths were reported.