Witnesses described seeing a man with a large knife, and passengers hiding in the toilets to escape the rampage, The Times reported.
One witness told the paper there was “blood everywhere” and people were getting “stamped” on by others as they tried to flee.
“I heard some people shouting ‘We love (you)’,” the witness said.
The attack is understood to have started shortly after the LNER train left Peterborough station.
Video footage on social media showed scores of blue-light police cars and emergency vehicles in a station car park, and a team of armed police running towards the stationary train at Huntingdon station.
