British police say 10 people have been taken to hospitals after a mass stabbing attack on a London-bound train, nine of them with life-threatening injuries.

In a statement early Sunday, hours after the attack, British transport police also said the incident has been declared a “major incident” and that counter-terrorism police are supporting the investigation.

“Ten people have been taken to hospital with nine believed to have suffered life-threatening injuries,” it said. “This has been declared a major incident and Counter Terrorism Policing are supporting our investigation whilst we work to establish the full circumstances and motivation for this incident.”

The attack took place as the train headed south towards Huntingdon, a market town a few miles northwest of the university city of Cambridge, early Saturday evening.

British Prime Minister Keir Starmer said his “thoughts are with all those affected” after the “appalling incident.”

A train is seen at a station.A train is seen at a station in Cambridgeshire following a stabbing attack onboard. (Chris Radburn/PA/The Associated Press)

Emergency services, including armed police and air ambulances, were quick to arrive on the scene shortly after they were alerted after 7:30 p.m. as the train arrived at the station.

British transport police, which took the lead on the response given it is responsible for security matters on the trains, said “multiple people” were stabbed on the Doncaster to London King’s Cross train as it headed into Huntingdon. It did not provide a motive for the attack.

Cambridgeshire Constabulary, the local police force, said armed police attended after officers were called to the scene at Huntingdon station at 7:39 p.m. on Saturday. It added that the two people were arrested at the station, which is around 120 kilometres north of London.

Paul Bristow, the mayor of Cambridgeshire and Peterborough, said he had heard of “horrendous scenes” on the train.

London North Eastern Railway, or LNER, which operates the East Coast Mainline services in the U.K., confirmed the incident had happened on one of its trains and urged passengers not to travel because of “major disruption.”