Police are investigating after an elephant was hit repeatedly in the head so hard with a hook that his legs collapsed.

The 18-year-old jumbo named Chan Chao was preparing to give tourists rides when the mahout launched the frenzied attack in Ayutthaya, Thailand, on April 11.

Footage shows how the rider used all of his strength to smash the metal bar with a sharp hook on the end at least 12 times into Chan Chao’s skull.

The bull was so stunned by the blows from the ‘bullhook’ that he stumbled on the ground then collapsed. He was left with deep wounds across the thick leathery skin on his head.

Footage of the distressing incident was taken by a tourist who said they were ‘appalled’ by the treatment and ‘left in tears’. They did not want to be named but said they ‘just want the elephants to be treated kindly’.

Staff at the Ayutthaya Elephant Palace where the cruelty happened have since sacked the mahout, named only as Peerapat, 18, while animal rights groups have filed a complaint at the local police station.

Police Lieutenant Samart Raksasak said today that officers had received the video and started an investigation.

He added: ‘The person in the video will be interviewed as well as witnessed and officers will check the elephant for injuries.’

Animal rights group Watchdog Thailand, who made a police complaint, said the case showed ‘serious violence’ against elephants.

A spokesman said: ‘The owner of the camp has removed the young man seen in the video, but we believe that fundamental improvements need to be made.

‘Serious violence against the elephant can be seen in the clip. We hope to see improvements in animal welfare management at the elephant camp and we will follow up the outcome of the investigation.’

The controversial attraction in the former capital of Thailand uses dozens of elephants dressed in red and gold robes to give tourists rides through the town. Visitors can also feed the creatures.

Elephants were seen last month with blood dripping from open wounds on their head from apparent blows from the hook - but it is rare to see such violence in public and captured on video.

Following the incident, the mahout claimed that Chan Chao was ‘tense’ because he had encountered another adult elephant moments earlier.

Peerapat said he used the tool, known as a bullhook, to control Chan Chao and prevent him from becoming aggressive.

He was later grabbed by the scruff of the neck by the camp's manager and forced to kneel at the elephant's feet and say sorry.

Peerapat told local media: ‘I’m very sorry about the incident and I admit everything. My father worked here and I have grown up with Chan Chao since we were both babies.

‘Using the hook is not done often, but only when the elephant is stubborn. If they are not controlled, in the future they will become fierce.’

Veterinarian Thongthae Meephan, the manager of the attraction, claimed that the wounds on the elephant’s head would be ‘healed in under a week’.

She said: ‘It was my mistake for putting a young inexperienced mahout in charge of Chan Chao. They grew up together so they have a connection but he shouldn’t use the hook so aggressively.

‘The hook is to control elephants if they show aggression, but the rider should not let their own emotions take over. They need to stop once the elephant has obeyed.’

Thailand has an estimated 2,000 Asian elephants living in the wild and a similar number in captivity where they work in zoos, camps, sanctuaries, or hired out for religious festivals and weddings.

Defenders of the use of elephants in the tourist industry claim that it is part of the country's historic culture and that the beasts are well cared for.

However, animal rights group PETA has long campaigned for a ban and boycott of anywhere 'exploiting' elephants or other animals in the tourist industry.

Vice President Jason Baker said: 'Elephants used in the tourism industry are often taken from their homes and frantic families when only babies.

'These traumatized animals are regularly beaten into submission with metal-tipped bullhooks so that they can be forced to give rides or perform ridiculous tricks for tourists.'