Emergency services have rushed to the scene at Huntingdon train station after a stabbing attack on a train travelling in Cambridgeshire.
Police can be seen running on the platform alongside a stopped train while multiple ambulances arrive at the station.
Authorities later confirmed 10 people were taken to hospital, including nine believed to have life-threatening injuries.
Two people have been arrested, Cambridgeshire Police said, and counter-terrorism officers have joined the investigation.