One man was arrested in relation to the incident, but those believed to have been seriously injured in the attack disappeared shortly afterwards and had not been seen by local hospitals.

A 22-year-old Theodore man was arrested at the scene shortly after the incident, during which both victims sustained potentially serious wounds.

According to police, a 22-year-old man was asked by staff to leave a nightclub between London Circuit and Alinga Street about 3am. There was a brawl on the footpath between the three men before the 22-year-old allegedly produced a knife and slashed one victim across the head and then stabbed another man.

Police arrived and arrested the alleged offender, also seizing the weapon.

But despite apparent serious injuries, police were unable to find the two injured in the attack who, by Saturday night, had still not presented themselves for medical treatment.

''All local accident and emergency departments in the ACT have been contacted and given the potential seriousness of the wounds, police hold concerns for the health and welfare of the victims,'' ACT Policing said.

The offender was being held in the ACT Watch House and is likely to face a charge of possessing an offensive weapon with intent.

Police said they were anxious to make contact with the victims involved as soon as possible, and urged anyone with information about their whereabouts to come forward and report it to police.

Anyone who saw the incident, or who can otherwise assist the investigation, should contact Police Operations on 131 444.