Detectives are investigating two suspected gay bashings in inner Sydney over the weekend, prompting a warning from police less than a fortnight before the annual Sydney Gay and Lesbian Mardis Gras Parade.

The NSW Police spokesman on Sexuality and Gender Diversity, Superintendent Tony Crandell, said the occurrence of two "bias-related assaults" over one weekend was uncommon, and was of concern to police.

One of the victims, Dylan Souster, 22, said he was punched in the face by a man who called him "a queer" outside his apartment block in Waterloo in the early hours of Sunday morning.

That man had initially been trying to help him, after he was earlier knocked unconscious by a group of young people and woke up in Waterloo Oval.