A 57-year-old man was slashed during a fight with another man on the subway in Lower Manhattan early Thursday, cops said.

The violent encounter unfolded around 5 a.m. on the northbound 4 train at the Fulton Street stop, where the argument between the two straphangers became physical, according to NYPD.

Cops said a 32-year-old man pulled a blade and slashed the victim’s left arm and stomach.

The attacker took off, and the victim was treated at Bellevue Hospital for his wounds, according to police.

Police said the men knew each other.

The knife attack came hours after a 54-year-old woman was slashed in an unprovoked attack on a platform inside the 14th Street-Union Square station.