Afghan Taliban leader Mullah Mohammad Omar has issued a rare public statement hailing the exchange of five Guantanamo Bay detainees for a Taliban-held US soldier as a "big victory".

Sgt Bowe Bergdahl, 28, was handed to US forces in Afghanistan on Saturday.

US Defence Secretary Chuck Hagel has defended the exchange amid criticism Congress was not given 30 days' notice before the detainees were released.

David Loyn reports.