One person has been seriously injured following a three vehicle crash in Royalla this evening.

At about 6.15pm, ACT Emergency Services responded to reports of a crash at the intersection of Old Cooma Road and the Monaro Highway.

Emergency services arrived to find one vehicle upside down in the middle of the roadway.

ACT Ambulance Service Intensive Care paramedics worked to stabilise the man and he was transported to hospital with serious condition.

Another person was assessed by NSW Ambulance Service paramedics and transported to hospital in a stable condition.

Two other people involved did not require transport to hospital.

The Monaro Highway was reduced to contraflow for several hours while police investigated the scene and the accident was cleared.