A Taliban spokesperson says five members of the Afghan Taliban who were freed from the United States military prison at Guantanamo Bay, in exchange for captured US Army Sergeant Bowe Bergdahl, have joined the insurgent group's political office in Qatar.

That means they will now be among Taliban representatives negotiating for peace in Afghanistan, spokesman Zabihullah Mujahid told The Associated Press.

After drawn-out negotiations, the five Taliban were released in 2015.

Bergdahl, who had been held in Taliban custody since 2009 when he wandered off a US army base, was given a dishonorable discharge last year and fined $1,000 on charges of desertion and misbehavior.

The stature of the five, which includes an ex-army chief, would make a peace deal palatable to the rank and file, says former Taliban diplomat Abdul Hakim Mujahid.