Police have launched a hunt to find a person suspected of firing an air rifle at a packed commuter train.

Passengers were left terrified after what detectives believe to be an air rifle or a stone was aimed at the window of a Southeastern service from Cannon Street to Gillingham in Kent.

Detectives have now launched an appeal as they revealed that whoever aimed the object remains at large after the incident near Greenhithe at about 6pm on Thursday.

A British Transport Police spokesman said: “Luckily no one was injured, but this could have been very serious.

“This sort of behaviour is extremely dangerous and this offence could have easily resulted in seriously injuring a passenger, not just considerable damage to the train, which as a result had to be taken out or service to be fixed.”

He added: “We searched the area immediately after the incident but to no avail, and would encourage anyone with information that could assist our investigation to come forward.”

Rail operator Southeastern had tweeted that its services were delayed “due to the drivers’ cab being shot at”. It later confirmed that it was in fact the front carriage of the 17.06 service via London Bridge which had been targeted.

Passengers told how the object had flown “centimetres” past them during the terrifying incident.

Adam Watts said: “I was on the train looking out the window about to get off at Greenhithe when I saw a flash followed by a smash and bang within a split second.

“It took a few seconds to register but then I saw the hole and realised what it all was, then frantically started patting my body in case it hit me and I had a delayed reaction."

Police asked anyone with information to contact them on 0800 40 50 40 or text 61016, quoting incident 432 of 29/10/2015.