A spokesman for the national intelligence agency, Sayed Ansari, said that Muhammad Hanif, who often contacted the media to deliver messages on behalf of the Taliban, was arrested in the border town of Torkham after arriving from Pakistan.
Two people traveling with him were also detained.
A previous individual who purported to speak for the Taliban, Mufti Latifullah Hakimi, was captured by Pakistani authorities in October 2005.
At least a dozen people have, at various times and sometimes concurrently, claimed to speak on behalf of the Taliban since the announcement in 2003 of the creation of a Taliban "leadership council."
(AP, AFP)