A 35-year-old man is in police custody following a suspicious unit fire in O'Connor overnight.

At around midnight ACT Fire & Rescue responded to reports of a building fire on Moorhouse Street.

Three units were well alight and fire-fighters from five stations worked to prevent fire spread to other units. Three units were impacted by flame, smoke and heat damage.

ACT Policing raced to the scene ensure everybody had escaped the structure.

ACT Policing is investigating the incident with the assistance of ACT Fire & Rescue and the man has been charged with arson.

An ACT Police spokesperson said: Several people who were observing the fire were treated for smoke inhalation by ACT Ambulance Service paramedics.

The man will face a bedside hearing this morning where police will oppose bail.

Anyone with information that could assist police is urged to contact Crime Stoppers on 1800 333 000, or via the Crime Stoppers ACT website. Please quote reference 6875922. Information can be provided anonymously.

If you experience, see or hear family violence occurring call Triple Zero (000) in an emergency or life threatening situation. For non-urgent police assistance call on 131 444.