The Taliban say the new leaders are committed to the armed struggle
The Afghan Taliban say Mullah Omar has named two new deputies after the arrest of his military chief in Pakistan.
Abdul Qayuum Zakir and Mullah Akhtar Mohammad Mansoor succeed Mullah Abdul Ghani Baradar, who Pakistan is holding.
The aim was to send "a message that one arrest will not affect our movement", a senior Taliban leader said.
Mullah Baradar was detained in Karachi in February in what was seen as a blow to the militants as they gear up to face a major Nato offensive this year.
The militants at first denied Mullah Baradar had been caught but the Taliban spokesman, speaking by telephone from an undisclosed location in Afghanistan, confirmed the arrest.
"Such arrests will not deter us from carrying on our activities," he told Newsweek magazine.
Recent media reports have suggested that Mullah Baradar supported talks aimed at some kind of peace deal in Afghanistan and that he had met intermediaries from the UN.
But the Taliban spokesman said both new deputies opposed talks with US-led Nato forces or the Afghan government - and were committed to carrying on the armed struggle.
Both new Taliban deputies are seen as vital figures in managing the movement's activities in what could be a pivotal year in the Afghan war.
The US is pouring in thousands of men as part of a troop "surge" before a withdrawal begins next year.
Abdul Qayuum Zakir, a former inmate at the US detention facility at Guantanamo Bay, is thought to be about 30.
He is said to be very popular with the younger generation of Taliban fighters because of his willingness to fight on the ground beside his men - especially along the new front in Kandahar and Helmand provinces in southern Afghanistan.
Reports say Abdul Qayuum Zakir was detained in Guantanamo Bay until 2007 and then deported to Afghanistan before being freed in 2008.
Soon after his release, he was back amongst his old comrades and has risen swiftly up the ladder.
Taliban militants who have been imprisoned in Guantanamo, or Bagram base in Afghanistan, are held in awe by their comrades, correspondents say.
While Abdul Qayuum Zakir is valued by the militants as a field commander, Mullah Akhtar Mohammad Mansoor is seen as a key behind-the-scenes leader.
In his 40s, Mullah Mansoor was part of the original Taliban leadership prior to the attacks of 11 September 2001.
Reports say he has been instrumental in managing Taliban logistics and raising funds, especially from the Gulf states.