A popular bar at Howard Smith Wharves has been damaged by a fire in the early hours of Saturday in what is believed to be an arson attack.

A Queensland Fire and Emergency Services spokeswoman said a crew was sent to the Brisbane precinct at 4.30am when an automatic fire alarm was activated at Mr Percival's.

Police investigate a fire at Mr Percival's bar at Howard Smith Wharves in Brisbane. Credit:Jocelyn Garcia

"It was followed by multiple triple-zero calls about the restaurant while en route," she said.

"Upon arrival, our response was upgraded to include five crews, wearing breathing apparatus, to battle the blaze."