The 13-year-old boy was assaulted on a bus near Hereford city centre.

The incident happened just before Christmas, but the details have only just been released by West Mercia Police.

Officers are urging a woman, aged in her late 20s, who they believe witnessed the attack, to come forward.

Inspector Steve Owen, from West Mercia Police, appealed for help in tracing the boy's attacker.

"This is something that we're ever conscious of, not just crime, but also anti-social behaviour on public transport," he said.

"We work closely with bus companies to try and combat the problem and are keen to hear from anyone who witnesses such incidents."