A 24-year-old man dressed in Batman’s Joker costume attacked passengers on a Tokyo train line on Sunday evening, injuring about 10 people as many party-goers headed into the city centre for Halloween gatherings, media reported.

Police arrested the suspected attacker on the spot, media reported. A man in his 60s was unconscious and in critical condition after being stabbed, while witnesses also said the attacker had spread fluid around the train and started a fire, according to media.

One video uploaded on Twitter and broadcast on NHK showed a steady stream of people running away from a train car where, seconds later, a small explosion caused a fire. Another video showed passengers rushing to squeeze out of the train’s windows and onto the platform where the train had made an emergency stop.

“I thought it was a Halloween stunt,” one witness told the Yomiuri newspaper, recalling the moment he saw other passengers running in a panic towards his train car. “Then, I saw a man walking this way, slowly waving a long knife.” He said there was blood on the knife.

The attack occurred on the Keio express line bound for Shinjuku, the world’s busiest rail station, at around 8 p.m. (1100 GMT), media said.

Partial service on the Keio line remained suspended late on Sunday, when Japanese voters went to the polls in a lower house election. TV footage showed scores of firefighters, police and emergency vehicles outside the station where the train had stopped.