Police said they were called to the Civic Pub on Lonsdale Street about 10.20pm.

"A 40-year-old man was treated by ACT Ambulance Service paramedics at the scene and subsequently transported to hospital," police said in a statement.

"A number of witnesses are assisting police with their enquiries, however no arrests have been made at this time."

Police want to talk to anyone who saw the incident but who has not yet spoken to them. They ask anyone with information to contact Crime Stoppers on 1800 333 000, or via the Crime Stoppers ACT website. Please quote reference 6429125.