Fire damages Canberra heritage building

An historic Canberra building has been damaged by a fire that followed an explosion in a popular restaurant.

A fire in a heritage Canberra building started after an explosion was heard at a restaurant. (AAP)

Fire has extensively damaged a heritage building in Canberra's CBD.

Firefighters were called to the historic Sydney building on Monday morning after an explosion in a popular restaurant.

Five fire trucks and hazardous materials crews fought the blaze, and were still monitoring hot spots in the afternoon.

The ACT Emergency Services Agency said most of the damage was inside the building and several businesses were affected.

The area, including the Civic bus interchange and nearby road London Circuit, was likely to remain closed for several days.

Two women were checked for smoke inhalation but did not need to go to hospital.