This is the hilarious moment two panda bears accidentally bumped heads after getting startled by their keeper coming inside, and then leap into a defensive stance in which they protect each other's backs.

Footage shows the hilarious mix-up during a visit at the Chengdu Giant Panda Base, in Sichuan Province, south-western China.

The video shows the panda siblings happily munching on bamboo shoots while sitting opposite one another.

Suddenly, their keeper is heard opening the door to throw in some more delicious bamboo which frightens the bears.

Both jump up at the same time and accidentally smack each other's heads in an attempt to face the source of 'danger'.

Still confused by the sudden noise, they quickly shake off the bump and roll towards opposite sides, with their backs turned to each other as they both stand on alert.

Visitors are heard laughing in the background when another loud bang - again coming from the keeper - startles the panda seen standing on the right. At that moment, the other bear seems to finally notice the employee tossing food their way and the two head for the door as the footage cuts.