Hack attack at Union Sq.

A man was slashed in the head — possibly with a machete — during an attack at Union Square Friday, officials said.

The 33-year-old victim was jumped outside a Food Emporium on Union Square East near Fourth Ave. — just steps from Union Square Park — at about 11:10 a.m.

He was attacked by his girlfriend's brother, according to a law enforcement source with knowledge of the case, who described the assault as a “domestic incident.”

The assailant was wielding a large knife or a machete, according to initial reports.

The victim, who is homeless, suffered a deep cut to the head and was taken to Bellevue Hospital for treatment.

His attacker ran off and was still being sought by police.