An investigation has been launched after a pack of hunting hounds strayed on to a railway track and were struck by a train.

A number of the animals were killed in the incident, which happened on the Norwich to London line at Great Moulton, near Diss, at 8.45am on Monday.

The dogs, from the Dunston Harriers hunt, were not hunting at the time, but were being exercised by staff on foot, near the railway line.

A group of the hounds got away from the main pack and tried to cross the tracks, where they were struck by the train.

A spokesman for the British Hound Sports Association (BHSA) said around six animals had got onto the line.

One passenger, who was on the London-bound service, said: "It’s absolutely heart-breaking, it’s beyond belief.

"When we first hit them it sounded more like lots of branches, I thought they might have fallen on the tracks.

"Then the train came to a stop and the driver said we’d hit a pack of hounds.

"There was a little wait and then we were moving again and the driver said it was a large number of dogs."

The train halted at the scene for a short time before moving on.

Following the incident, the next service from London Liverpool Street to Norwich, which was due to leave at 11am, was cancelled.

Greater Anglia said its train had been damaged during the incident, which it was now investigating.

A spokeswoman said: "Greater Anglia and Network Rail are currently investigating how the dogs came to be on the tracks."

A spokesman for the BHSA, which represents hunts, said: “We understand an incident occurred whilst the Dunston Harriers were being exercised on foot by their professional hunt staff.

"Six hounds strayed away from the rest of their pack and although no members of the hunt were present at the time, we understand some of those hounds were subsequently fatally injured during a collision with a train.

"Our thoughts are with the driver of the train and anybody who may have witnessed this distressing incident and also with the hunt staff who devote their lives to looking after these hounds on a daily basis and care deeply for every one of the pack.”

Nick Weston, from the anti-hunt campaign ground the League Against Cruel Sports, said the "tragic" incident "highlighted the irresponsibility of hunts".

He said: “The hunts are risking the safety of their hounds and causing stress to passengers and train drivers who would be witnessing extremely distressing accidents.”

The crash has also been reported to British Transport Police (BTP).

A spokesman for the force said: "British Transport Police received a report of dogs on the tracks near Great Moulton at 9.07am today. Trains passed through the location on caution for a short time. There were no further sightings of dogs on the railway."