An elephant who appeared in Thai films and television adverts has crushed its owner to death at a zoo in the northern city of Chiang Mai.

The elephant, believed to be in musth - an aggressive state associated with a surge in testosterone - attacked his 54-year-old owner, Somsak Riengngen, crushing him to death with his trunk.

The accident occurred on Monday morning as the elephant was unchained, the South China Morning Post reports.

The five-tonne elephant, named Ekasit, had one mahout, or handler, on his back and reportedly took a few steps before turning and attacking Somsak who was on the ground.

“The elephant suddenly turned back and used his trunk to grab the victim. Then the elephant used his trunk to crush him,” Wuthichai Muangman, acting director of Chiang Mai Zoo, told the Post.

Mr Wuthichai described Somsak as an “elephant expert”, but added that the elephant had been in musth when the accident happened.

During musth, which often occurs during winter, male elephants can experience surges in testosterone that can send levels of the hormone up by 60 times the usual amount.

Even the most placid elephants can become very violent.

The state of musth in male elephants has often been linked to the rutting season, however, any relationship with reproducing is far from clear, as female elephants’ reproductive cycle is not seasonally linked as the musth is. Also, bull elephants in musth have been known to attack females regardless of whether they are in heat or not.

Ekasit the elephant had appeared in television commercials as well as several foreign and Thai films.

He was being kept at the zoo in Chiang Mai as part of a contract that was due to expire in April.

The zoo owner’s death has reignited the debate about captive wild animals in Thailand.

The country is infamous for offering tourists rides on elephants that are inadequately cared for.

Out of 2,923 elephants documented as working in Asia’s tourism trade, 2,198 are in Thailand, notes the South China Morning Post.