Provincial Police Commander for North Fly command, Silva Sika, said the victims had been operating shops in the Lake Murray area for some months when they were killed.
The reason behind the killings is yet to be established.
PPC Sika said the three suspects, believed to be from Hela Province, were captured and are now in police custody.
Fourteen police personnel, including CID from the North Fly district, assisted police in Middle Fly to apprehend the suspects.
The suspects are now at the Daru police station lock up, awaiting court mention.