An argument over a woman turned deadly when a man fatally knifed his lover’s ex-beau, police sources said.

The assailant clashed with his girlfriend’s former boyfriend on Crown Street near Nostrand Avenue yesterday and a knife fight soon broke out between

the rivals, police sources said. During the struggle, the 37-year-old victim was stabbed in the torso after slashing the suspect at 10:31 p.m., police said.

After the stabbing, the 45-year-old suspect ran up to his girlfriend’s home and the woman called 911.

Responding police rushed the men to Kings County Hospital, where the victim was pronounced dead. The suspect is being questioned by police.