A maniac on a downtown Manhattan subway ignited a cup of flammable liquid Saturday afternoon, then threw it at a stranger, causing the man’s shirt to ignite and burning his chest and neck, cops said.

The firestarter fled from the train after the terrifying, unprovoked attack, authorities said.

The incident unfolded as the No. 1 train was pulling into the Houston Street Station at West Houston and Varick Street around 2:45 p.m., when the attacker flicked his cup at the rider, who appeared to be in his 20s.

When the doors opened, the attacker ran from the train but stopped to scoop up a phone that a female on the platform had dropped.

Quick-thinking police officers talked to her and tracked the phone. They arrested the firebug nearby, cops said.
The burned man was treated for minor injuries at New York Presbyterian-Weill Cornell Hospital.