Daniel Wood, 32, attacked the teenager while they were both staying at a hostel for homeless people.

A court heard the teenager had made it clear he was not interested in having sex with Wood, who had been drinking, but was molested and had a sex act carried out on him.

Wood struck again elsewhere a few months later, taking advantage of another young man while the victim was sleeping.

Wood, who was on bail at the time of the offences, pleaded guilty to two charges of sexual assault.

At the High Court in Edinburgh on Tuesday, Lord Harrower said: "Each incident involved acts of serious sexual violence."

Wood, formerly of Aberdeen, preyed on his victims at addresses in the city and in Banff, Aberdeenshire.

He attacked the teen in August 2020 and then sexually assaulted the other man in the November of that year.

Lord Harrower said: "I have been provided with a statement from the victim of the second offence, from which it is clear that your behaviour has caused him great psychological and emotional harm.

"In these circumstances, I am satisfied that only a substantial sentence of imprisonment will reflect the need for both retribution and deterrence."

Lord Harrower said Wood would have faced a 52-month jail term had it not been for his guilty pleas.

He pointed out the pleas were made shortly before a trial and both victims had already given recorded evidence by that stage.

Read more from Sky News:
Brothel keeper who made £167,000 only has £822 to hand back
Lawyers for rapist fight to get conviction quashed
Man who raped and murdered mother-of-two given lighter sentence

The judge also noted Wood refused to cooperate in the completion of psychiatric reports.

Lord Harrower said: "The result is that I still do not have before me any formal assessment of your mental state."

Defence counsel Jonathan Crowe told the court he was not suggesting a mental health disposal should be made in Wood's case.

He said at the time of the offending Wood was unemployed and living in homeless accommodation.

He said Wood had been drinking and on reflection considered the level of alcohol consumed by him impaired his judgement.

Mr Crowe said: "He wishes to offer a full public apology to the complainers involved. He acted in a way that was completely unacceptable."

As well as the prison sentence, Wood was also placed on the sex offenders' register indefinitely.