FIVE teenagers have been arrested in what has been described as a "terrifying" incident on Irish Rail.
The incident occurred on the 5.55pm inter-city service from Heuston Station in Dublin to Newbridge in Co Kildare yesterday evening.
It is understood that two passengers were assaulted by a group of up to four youths shortly after the train left Heuston Station at 5.55pm.
Two male passengers were allegedly struck, including one who suffered a possible broken nose.
Passengers who witnessed the incident immediately called emergency services, but the driver did not know until after the alleged culprits exited the train at Sallins in Co Kildare.
Gardai later attended the station, but the group had already managed to get away.
A spokesperson for Irish Rail confirmed that there had been an incident on the service, and apologised to all passengers on board.
"We would apologise to anybody onboard who obviously wouldn't expect to be subjected to this when they are on their way home from work," they said.
They added that the company was investigating the incident and that the train was not delayed.
A number of passengers took to Twitter to express their shock over the incident.
"Feel very unsafe with no staff on train. Routine anti-social behaviour goes unpunished and escalates," one user tweeted.
Another said: "Never been so scared on a train in my 14 years commuting. Totally unacceptable that nothing was done. Passengers were terrified."
Gardai last night said they were also investigating the incident, but that the passengers who were allegedly assaulted had yet to come forward.
It is the second violent incident to take place on an Irish Rail service in a week, after two people were arrested when windows were smashed on the 5.40am Longford to Dublin service last Friday.