A group calling itself the Ossetia Jamaat made the claim in a statement posted on September 13 on a separatist Chechen website.
The group said they shot down the helicopter with a shoulder-fired anti-aircraft missile after receiving intelligence about who was on board and the route of the flight.
The Mi-8 helicopter was transporting high-ranking officers when it crashed near Vladikavkaz.
Prosecutors in North Ossetia said they had no previous knowledge of the group.
The Russian military has said the helicopter crashed after it flew into a cloud and the pilot apparently lost control. But prosecutors said investigators were looking into all possible causes, including a possible attack by militants.
(chechenpress.info, lenta.ru, Ekho Moskvy)