A viral video has captured the terrifying moment when a lion attempted to attack a two-year-old boy at the Chiba Zoological Park in east Tokyo.

The boy, who had been observing the big cat through the safety glass, is seen turning his back to face the camera.

Within seconds, the lion - estimated to weigh over 180kg - bounded from the far end of its enclosure to the boy, slamming into the glass as it pawed at the child.

Keepers at the zoo claimed that the lion was playful and had previously did the same to other children, reported Japan news agency NTV News24.

The video comes days after an endangered gorilla was shot dead at the Cincinnati Zoo in the United States in order to protect a three-year-old boy who had somehow ended up in its exhibit.

The zoo's gorilla exhibit was remodelled to incorporate a new barrier so as to avoid a repeat of the incident.