Police are investigating after homophobic graffiti, calling for violence against gay people, was found plastered across a wall in Sydney's inner west.

Laura Hunter and April Long were travelling through Alexandria on Sunday morning when they saw an older man crouched and spray painting the wall.

The pair confronted the man and saw the message, which reads "Bash a gay today".

Ms Hunter photographed the offending message and the man as he pulled a hat down over his eyes and walked away.

The man said he had been "robbed by a gay man once", Ms Hunter said on Sunday.