Hakimullah Mehsud is believed to be in his late 20s
Pakistan's Taliban movement has named a new leader, its deputy head Maulvi Faqir Mohammed has told the BBC.
He said Hakimullah Mehsud, a close associate of ex-leader Baitullah Mehsud, had been unanimously appointed at a meeting in northern Pakistan.
Pakistani and US officials believe Baitullah Mehsud was killed in a US drone strike in early August.
However the Taliban continue to insist that he is still alive, despite their decision to appoint a new leader.
Hakimullah Mehsud, who is in his late 20s, is a military chief of the Tehrik-e-Taliban Pakistan (TTP) organisation formed by Beitullah Mehsud in an effort to unite the various factions under one umbrella.
He controls an estimated 2,000 fighters in the Orakzai, Kurram and Khyber regions.
'Ruthless and rash'
The announcement by Maulvi Faqir Mohammed follows weeks of speculation, and rumours of shootouts and disarray in Taliban ranks.
Some deny Baitullah Mehsud is dead
"Baitullah Mehsud, has been in hiding and he is very ill. He expressed his will that the next Taliban chief should be elected by the Taliban Council while he is alive," Mr Mohammed told BBC Urdu.
"The council held its meeting in the Orakzai tribal area... the council has decided that Hakimullah Mehsud will be the leader of the Tehrik-e-Taliban Pakistan," Mr Mohammed said.
But the BBC's Orla Guerin in Islamabad says many will see the naming of a new leader as confirmation that Baitullah Mehsud is dead.
Our correspondent says Hakimullah Mehsud is a young commander in Baitullah's own image, and is reported to be equally ruthless.
Some believe he could be an even bigger threat to Pakistan, and to foreign troops across the border in Afghanistan, she adds.