Pakistani officials say the army has arrested a man they believe to be chief spokesman for the Pakistani Taliban, BBC reported.
Maulvi Omar, spokesman for the Tehrik Taliban Pakistan (TTP), is said to have been a key aide to Baitullah Mehsud, thought to have been killed recently.
He was reportedly picked up while travelling in a tribal area by car close to the Afghan border.
Pakistani officials were expected to make a formal announcement of his arrest later on Tuesday.
"A very, very important militant has been arrested," Major Fazal Ur Rehman, told the AFP news agency.
Mr Rehman said the detainee would be presented before journalists at a press conference in the tribal Mohmand region.
Earlier this month, Pakistani officials said they had "credible evidence" that Baitullah Mehsud - described as the head of the Pakistani Taliban - had died in a US drone attack.
But correspondents say the situation is very unclear and information is based on rumours from deep inside militant territory in north-west Pakistan
Maulvi Omar comes from Bajaur, a tribal area where the Taliban established themselves early on.
Pakistan Taliban spokesman 'held'
