A 21-year-old man was slashed in the back of the head during a dispute on a Brooklyn train Monday morning, cops said. 

The victim was on a northbound J train at the Alabama Avenue station at about 6:50 a.m. arguing with three people when one of the trio cut him, police said. 

He was taken to Interfaith Medical Center with a laceration, cops said. 

It did not appear the victim knew his attackers, said to be a woman who appeared to be in her 30s and two men in their 40s.

No arrests were immediately made. 

The incident comes amid multiple recent attacks in the city’s subway system.

Recent victims include a woman who was slashed while feuding with a man at the Fordham Road station in the Bronx, and an ex-cop who was slashed by an attacker who first spat at him and his wife at the Wall Street station in Lower Manhattan.