Detectives from Strike Force Buckeridge, a unit dedicated to investigating the alleged sexual and physical assault, arrested the 28-year-old man outside a home unit in Jindabyne just after 9am on Tuesday.

Investigators also executed a search warrant at the unit and seized a number of items.

Police were called to Kosciuszko Road about 1.30am last Thursday after reports a 22-year-old woman and a 25-year-old man had been assaulted.

The pair, friends from northern NSW, were walking towards a hotel after leaving the Banjo Patterson Hotel about 1am.

The suspect allegedly set upon the pair, punching the 25-year-old man in the head and knocking him unconscious, before physically and sexually assaulting the woman.

Police said when the 25-year-old regained consciousness, he tried to help his friend but was allegedly assaulted again.

He eventually flagged down a passing car and the alleged attacker fled.

NSW Ambulance paramedics treated the alleged victims at the scene for serious facial injuries, with the woman taken to Canberra Hospital and the man to Cooma Hospital for treatment.

They have both since been discharged, and the 25-year-old man returned to the scene with investigators on the weekend to walk them through the alleged assault.

At a press conference in Sydney on Tuesday afternoon, Detective Acting Superintendent Tom Barnes said while police initially believed more than one man was behind the alleged attack, investigators now believed they had "the sole person responsible" in custody.

The suspect was being held at Jindabyne Police Station on Tuesday afternoon, and Acting Superintendent Barnes said it was likely he would be charged and brought before Queanbeyan Local Court on Wednesday.

Acting Superintendent Barnes said he believed the 28-year-old Brit was working in Australia on a seasonal basis at a ski resort.