The Chinese-language Beijing News said tourist Zhang Jiao went into the enclosure Wednesday to chase a toy dropped his 5-year-old son and was attacked by Gu Gu, a 240-pound panda, Britain's The Sun newspaper reported Thursday.
Officials said Gu Gu clamped his jaws down on the man's legs, forcing zookeepers to use tools to pry the panda's mouth open.
The tourist suffered damage to his ligaments and was recovering from surgery Thursday.
Zookeepers said Gu Gu has attacked zoo visitors two times previously -- biting a drunken tourist who jumped into the pen in 2007 and a teenager who entered its exercise area in October.
Celebrity Families of 2014 [PHOTOS]