A "vulnerable" woman has been arrested on the Sea Cliff Bridge after the suspicious death of a woman believed to have been her ex-girlfriend outside a Zetland unit block on Monday night.

Emergency services were called to the rear of the unit block on Rose Valley Way, Zetland, about 8.45pm after the woman, 23, was found "suffering injuries on the footpath", NSW Police said in a statement.

Zixi Wang has been arrested over the suspicious death in Zetland. Credit:NSW Police

Redfern police officers at the scene attempted to revive her but were unsuccessful, the statement said.

Strike Force Deepfield investigators spent Tuesday looking for Zixi Wang, 29, also known as Jessie, who police say “has an outstanding warrant in relation to the matter”.