THREE boys frightened passengers on a bus in the Valleys when they hurled a large rock through its window.

Bus firm bosses say that two women from Risca were fortunate to receive only minor injuries after glass showered inside the bus from the smashed window.

The incident has shocked bus firm Stagecoach and local police because the culprits are believed to be under the age of ten.

The incident happened when the weekly Risca to Abergavenny service by Stagecoach was passing along Pond Row in Nantyglo at around 10.10am on Tuesday.

The three boys were seen throwing a rock at the passing bus before running off.

The two women from Risca who received slight injuries and the rest of the passengers were able to continue their journey to Abergavenny once a replacement bus had been arranged.

Mark Tunstall, operations manager for Stagecoach, said: "Thankfully, nobody was seriously injured but we are very lucky that was the case. "It was a very serious incident given the apparent age of those involved and the time of the day that it happened.

"We have reported it to the police with a view to them doing something about it.

"It is something we are not used to happening and I would very much hope people can identify who these people are because the potential consequences are far more serious than the actual consequences on this occasion, thank goodness."

Mr Tunstall said his bus drivers expect to deal with increased levels of nuisance behaviour over the summer holidays with kids being on holiday. He added: "This is not a run-of-the-mill incident for Stage-coach - especially at that time of the day. Youngsters must be made to realise they cannot do this type of thing."

PC Bob Ricketts, the crime and disorder officer at Brynmawr police station, said: "When you think of what could have happened this is certainly a serious incident.

"Had it hit the driver he could have crashed the bus and goodness knows what would have happened."

Police say they are investigating the incident. Anyone with information is urged to contact Brynmawr police station on 01495 310773.