A man has been found dead and dozens of residents were evacuated from an inner Sydney apartment block after a fire broke out in the building on Friday morning.

Emergency services were called to the unit block on George Street in Redfern about 4am on Friday following reports of an intense fire at the complex.

A spokesman for Fire and Rescue NSW said crews rushed to the scene with initial callers "reporting they could hear screaming".

On arrival, firefighters quickly identified "a top floor unit in a small unit block was totally engulfed in fire", he said.