A group of vandals wearing balaclavas have sprayed graffiti all over a DART carriage and threatened passengers with planks of wood.
They held back the carriage doors, and blocked the train from leaving Clongriffin at about twenty to eleven last night.
Barry Kenny from Irish Rail has described it as a deliberate and calculated attack.
"While we battle with graffiti all the time, we have never had anything of this scale", he said.
Other customers on board the carriage tried to move the gang away from blocking the doors, before being threatened by the gang and then calling Gardai.
"This is something we will be reviewing with Gardai, and we will also be putting security measures in place as a result", Barry Kenny explained.
Dublin Senator Aodhán Ó Ríordáin said last night's attack is "no surprise to the local community who have been reporting serious anti-social behaviour at Northside stations for months."
"It is now time to considered Garda policing on DART services and stations for a limited period of time to reassure passengers and to tackle this issue seriously", he said.