City Under Siege (simplified Chinese: 全城戒备; traditional Chinese: 全城戒備) is a 2010 Hong Kong science fiction action film directed, produced, co-edited and co-written by Benny Chan. The film stars Aaron Kwok, Betty Shu, Jacky Wu, Zhang Jingchu, and Collin Chou. The film follows a group of circus performers who goes on a rampage after an accidental exposure to chemical gas left by the Japanese army in World War II, granting them superhuman abilities.