A territorial pet pit bull mauled a worker after he wandered into the wrong house in Thailand.

The violent guard dog named Giant, 4, attacked the Thai-American victim Phonphap Adrien Athichad, 19, who had mistakenly trespassed into the residence in Samut Prakan province on October 8.

It sank its teeth into both of Phonphap's calves, leaving gaping wounds on his legs.

Garage workers who witnessed the incident called police and paramedics for help.

Knowing there were several pit bulls in the house, they had tried to warn the teenager from entering, but he was wearing headphones and could not hear them.

One employee said: 'The dogs started barking and one bit him in the legs. We called officials right away after seeing what was happening.'

Paramedics administered first aid to Phonphap before taking him to the nearest hospital for treatment.

Police said they tried questioning the young man but he would not talk about the incident.

A Phra Samut Chedi district police spokesperson said: 'The scene was a residence that also served as an office for a fuel company, with an area of over five acres.

'The victim appeared to be distracted when we found him. He was mumbling English words to himself.

'We tried questioning him in both Thai and English, but he wouldn't talk to us and only said that he was walking on the road and found it hard to explain.

'The dog's owner told us that he won't be pressing charges for intrusion and that he only felt sorry that the boy was attacked.

'We believe that Phonphap might have entered the wrong house. His relatives have already been informed about the incident.'