Three people, including a police officer, have been stabbed by a man wielding a knife at Manchester Victoria station.
The knifeman shouted "Allah" - the Arabic word for God - after the attack, a witness said.
Counter-terrorism police are now investigating the incident.
British Transport Police (BTP) said one of its officers was stabbed in the shoulder, and that a man and a woman - both in their 50s - had been taken to hospital with knife injuries.
The woman suffered injuries to her face and abdomen and the man was injured in the abdomen, police said.
The force described the injuries of all three as "serious but not life-threatening".
A man was been arrested at the scene on suspicion of attempted murder following the incident shortly before 9pm.
BTP and Greater Manchester Police remain at the station which is closed.
Sam Clack, a producer at the BBC who was waiting for a tram at the station, described the attack he witnessed: "I just heard this most blood curdling scream and looked down the platform.
"What it looked like was a guy with a woman of similar age and another guy all dressed in black.
"It looked like they were having a fight but she was screaming in this blood curdling way.
"I saw police in high-viz come towards him."
Mr Clack said that as the knifeman backed away from police, he came within several feet of him.
"He came towards me," Mr Clack said.
"I looked down and saw he had a kitchen knife with a black handle with a good, 12 inch blade.
"It was just fear, pure fear."
Mr Clack continued that he was so terrified that he too would be stabbed, that he considered jumping on the tracks to escape.
Mr Clack, who was catching a tram home, said police officers used a Taser and pepper spray before, "six or seven" officers jumped on the man.
The 38-year-old reported that when the suspect was held down by police he said: "'As long as you keep bombing other countries this sort of s*** is going to keep happening'."
BTP Assistant Chief Constable Rob Potts said that although the investigation was being led by counter-terrorism police, officers were keeping an "open mind".
He added that "there is currently no intelligence to suggest that there is any wider threat at this time".