An unidentified man was stabbed in the leg on a northbound 6 train yesterday afternoon. The victim staggered off the train at 14th Street-Union Square shortly before 5 p.m. and was rushed to Bellevue Hospital, where he's listed in stable condition.

It's unclear what preceded the stabbing, if anything. An NYPD spokesman tells us there is "no apparent motive" at this time; the assailant fled in an unknown direction and remains at large. Service on the northbound 6 train was disrupted for about an hour while investigators searched the tracks for the knife.

Earlier on Sunday, a man was stabbed to death on Staten Island. Police sources tell the Staten Island Advance that Durrell Finley, 26, approached an unidentified man who was returning home with beer and asked for one. When the man refused, a fight broke out at the corner of Harrison Avenue and Faber Street.

Sergio Carreto, a relative of the man with the beer, rushed to intervene, and allegedly stabbed Finley in the back with a kitchen knife. He was pronounced DOA at Richmond University Medical Center.

Carreto was arrested yesterday and charged with murder and criminal possession of a weapon.