Baitullah Mehsud has been blamed for a series of suicide attacks in Pakistan
The chief spokesman for the Taliban in Pakistan, who was arrested on Monday, has confirmed that the group's leader is dead, Pakistani officials have said.
A minister from North West Frontier Province said Maulvi Omar had stated that Baitullah Mehsud was killed in a US drone attack earlier this month.
The Taliban had previously denied US and Pakistani reports that he was dead.
Maulvi Omar was arrested in the Mohmand tribal area while travelling to South Waziristan, near the Afghan border.
Mr Omar was the second prominent Taliban figure to be arrested in 24 hours.
We will catch them all. All Taliban will have to face the same fate
Mian Iftikhar Hussain, North West Frontier Province minister
Qari Saifullah, a commander affiliated to Harkat Jihad-e-Islami, was detained while being treated at a private hospital in Islamabad, officials said, reportedly after being wounded in a missile strike.
Both men are still being questioned about their possible roles in militant attacks in Afghanistan and Pakistan, police said.
Meanwhile, three paramilitary troops were killed and another three injured in a suicide bomb attack on a Frontier Corps checkpoint outside the town of Miran Shah in North Waziristan, officials said.
Maulvi Omar was captured along with two associates in the village of Khawazeo in Mohmand on Monday night. Local tribal elders reportedly assisted the security forces.
Mr Omar comes from Bajaur, a tribal area in the North West where the Taliban established themselves early on.
Footage reportedly showing Maulvi Omar being arrested
He was the official spokesman for Tehrik-e-Taliban Pakistan (TTP), an umbrella organisation of regional and tribal-based Pakistani militant groups, and is said to have been a senior aide of Baitullah Mehsud.
Correspondents say his arrest is significant because Mr Omar had been acting as a liaison between the various Taliban groups and was a key figure in the Taliban's propaganda campaigns.
After his arrest, he was questioned by intelligence officials.
"Maulvi Omar has confirmed the death of Baitullah during interrogation," North West Frontier Province's Information Minister Mian Iftikhar Hussain told AFP news agency.
"We will catch them all. All Taliban will have to face the same fate," he added.
Maulvi Omar was photographed in detention in Peshawar
Pakistani and US officials have said that Mehsud was killed - along with one of his wives - in a US missile strike on his father-in-law's house in the Zangarha area, north-east of Ladha, on 5 August.
Two days' later, a shoot-out broke out between Mehsud's potential successors in Waziristan in which one of them was killed, they say.
Despite both sides' declarations, there has been no proof from the Taliban that Mehsud is alive or from the government that he is dead.
Believed to command as many as 20,000 pro-Taliban militants, Mehsud came to worldwide attention in the aftermath of the 2007 Red Mosque siege in Islamabad - in which the security forces confronted and forcibly ejected militant students loyal to him.
He has been blamed by both Pakistan and the US for a series of suicide bomb attacks in the country, as well as suicide attacks on Western forces across the border in Afghanistan.
The BBC's Aleem Maqbool in Islamabad says Pakistani ministers are confident the Taliban is under serious pressure and that its remaining leadership is in disarray.
But, our correspondent says, the militant infrastructure here has been built up over decades and the underlying problems which feed it - poverty and inequality - remain.
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