A “disgusting” sex offender has been jailed after targeting a teenager on a train.

The victim was walking through a carriage on a service to Sevenoaks with her friend when Petro Ninichuk grabbed her hand and pulled her to sit on the seat in front of him.

She told him she was only 15 in the hope it would stop his advances, but Ninichuk still brazenly sexually assaulted her in a prolonged attack, which took place on January 27 last year.

The victim’s friend approached another passenger, who intervened and invited the girls to sit with him.

When the train reached Sevenoaks, the victim’s friend alerted security staff who identified Ninichuk on the train.

While he was with security staff Ninichuk spotted the victim who had been taken to safety in the station office and was trying to get near her, telling them “that’s my girlfriend”.

The British Transport Police was called and he was arrested immediately.

On April 11, Ninichuk pleaded guilty to sexual assault at Inner London Crown Court.

The 37-year-old has been sentenced to 19 weeks in prison and ordered to sign the Sex Offenders Register for seven years.

Following the sentencing, Detective Sergeant Richard Osbourne said: “This was a truly disgusting and brazen sexual assault on a teenage girl, by a predator who knew full well she was just 15 years of age and chose to subject her to this prolonged attack.

“I’d like to pay particular praise to the victim and her friend for reporting it to station staff at the time which enabled us to act quickly, and also to the bystander who intervened at the time of the assault to remove them from the situation.

“We will always take reports like this extremely seriously as we did in this case, where BTP quickly arrived on scene and brought Ninichuk into custody.

“Please save our text number 61016 in your phone and let us know if you ever need us, and remember to ring 999 in an emergency.”