A bizarre video has emerged of a polar bear seemingly trying to eat a baby at St Louis zoo, USA.

The footage, shot on Monday, shows the bear diving close to a baby sitting in front of the enclosure glass.

The bear then catches his breath and dives again with its mouth wide open scaring the baby.

"The polar bear is over 1,200 pounds and was very active, which was highly unusual on a hot Summer day," the filmer wrote online.

The video was shot at 5:00 pm CDT at the St. Louis Zoo in St. Louis, MO. This particular polar bear is somewhat famous already, last year the polar bear was relocated to the St. Louis zoo and had to be quarantined for 30 days, and his exposure to the public was much anticipated and marketed. The polar bear is over 1200 pounds and was very active, which was highly unusual on a hot Summer day. It dove several times to get familiar with the location of the baby, and then decided to instinctually attack the baby.