A 19-year-old man has been arrested on suspicion of attempted murder after a stabbing on a train in south London.

British Transport Police (BTP) said they received reports of two men fighting between Beckenham and Shortlands railway station shortly before 4pm on Wednesday.

Footage shared on social media showed a male wearing a black hooded jacket, black trousers and a face mask holding a large blade, while onlookers could be heard telling him to stop.

A manhunt was launched and on Thursday BTP said they had arrested a 19-year-old man and recovered a knife.

The victim, who is in his 20s, was taken to hospital and is in a “critical but stable condition”.

Train services in the area were disrupted until around 6.30pm.

Superintendent Darren Malpas said: “We understand the concerns of the public following this incident and our detectives have been working tirelessly to investigate. I hope this arrest will bring some reassurance to those on the rail network.”

At just after 10.30pm on Wednesday, BTP also received reports of a man being stabbed on a platform at Kennington underground station, nearly nine miles away from the earlier incident, which is not believed to be linked.

Another man is thought to have been injured trying to stop the attack.

Both were taken to hospital and are in a critical but stable condition.

The suspect had left the area and no arrests have been made.