Two comedians in town for the Melbourne International Comedy Festival have been attacked - one bashed badly - after their friend was racially abused in the city.

Comedian Peter Morley in a picture taken immediately after the attack.

Melburnian Peter Morley, his partner Rachel Kottkamp, who both live in Los Angeles, and their African-American friend were sitting on a bench outside St Paul's Cathedral just after midnight on Tuesday after a night out when they were approached by a young Caucasian man seeking directions.

"I was trying to give him directions up to Russell and Bourke [streets] and he wasn't understanding me. Our friend told him to leave us alone, that we weren't able to help him. When she spoke up, that's when he got really upset. Partly because she's a woman, but definitely because she's black," Mr Morley said.

Mr Morley and Ms Kottkamp said he told their friend she was a refugee and "Go back the f--- to your own country".