A convicted drug trafficker killed a man in a hammer attack after the victim ran up a £200 debt he was unable to pay.

William Richardson, 35, formerly of Park Brae Gate, Ruchill, Glasgow, turned up at a house in Kelty, Fife, and went into a bedroom where Colin Oliphant had been resting.

He repeatedly assaulted him while others in the property heard Mr Oliphant say: "Sorry Willie, don't hit me, stop it Willie. What are you doing with that? Dinnae, dinnae."

The killer told him: "You know I am a boxer". He then punched him on the nose.

Richardson, who was jailed in 2013 for supplying heroin, drove off from the house with others and was described as acting "full of bravado", the High Court in Edinburgh heard.

Advocate depute Bill McVicar told the court: "The now deceased quickly began to struggle to breathe with his face swelling and asking for help, pointing to his neck."

An ambulance was called but the attack victim's face and throat continued to swell after he was placed in the vehicle. The swelling also spread to his arms, legs and body.

Mr Oliphant, 38, went into cardiac arrest and despite efforts to save him he died. The cause of death was later given as complications of chest trauma.

The prosecutor said the fatal injury inflicted on Mr Oliphant, a father-of-one, was a fracture of a rib on the left side of his back that had splintered bone and punctured a lung.

Richardson was originally charged with murdering Mr Oliphant in the attack on Keltyhill Avenue on September 6 last year.

He admitted a reduced charge of culpable homicide on Friday. He pleaded guilty to repeatedly punching the victim on the head and body and repeatedly striking him on the body with a weapon and killing him.

Mr McVicar said: "The deceased Colin Oliphant sourced cocaine for onward supply from the accused."

He said the victim had become indebted to Richardson due to his own use of drugs and was unable to pay what he owed.

After the assault, Richardson returned to a house in Ballingry, Fife, where he was living with a woman and told her the victim had been "causing issues at work", Mr McVicar said.

He later informed her the victim was dead and he appeared to be in a state of shock, the court heard.

He turned up at Dunfermline police station on September 8 and said he wanted to speak to detectives before telling an officer: "There were witnesses there. I've never done an assault before."

The judge, Lord Woolman, deferred sentence on Richardson for the preparation of a background report and remanded him in custody.