Gu Gu, the panda bear who is the star attraction at the Beijing Zoo, attacked a teenager who jumped into his enclosure Monday afternoon, according to a zoo official and published reports.

Eight-year-old Gu Gu and another bear were being fed when a 15 year old teenager, Li Xitao, jumped over a 1.4m barrier surrounding the pandas' outdoor exercise area. Gu Gu attacked the teenager, ripping chunks off his legs, said a zoo official who would only give his name as Zhang.

The attack lasted for about four minutes before Gu Gu's keepers, who have trained the bear to obey their command, managed to lure him away.

Medical officials reported that the boy was viciously attacked and his bones were showing through the chunks of flesh left around in the ambulance.

Zoo security officials said Li told them he had climbed into the bear enclosure out of curiosity. He was taken to Beijing Children's Hospital.

According to Associated Press, calls to the hospital about his condition were not answered.

This is not Gu Gu's first violent encounter with an interloper. Last September, he had bitten flesh off a drunken man's leg; the man had jumped into his enclosure to hug him and had retaliated by biting Gu Gu in his back.

Pandas, which are perceived by the general public as being cute, can become violent when provoked.