The Pakistani Taliban's ruling council met on Saturday to choose a new leader after a U.S. drone killed the former leader Hakimullah Mehsud, AFP reports.
Mehsud, who was under a $5 million U.S. government bounty, was buried late Friday after being killed when a drone targeted his car in a compound in North Waziristan tribal district, the report said.
The killing of its young, energetic leader represents a major setback for the Tehreek-e-Taliban Pakistan (TTP), a coalition of factions behind some of the most high-profile attacks to hit Pakistan in recent years.
But it also threatens the government's efforts to begin talks to end the TTP's bloody six-year insurgency that has left thousands of soldiers, police and civilians dead.
Interior minister Chaudhry Nisar slammed the U.S. strike as a "drone attack on the peace process", saying a team of religious clerics was about to meet the TTP with a view to starting peace talks when Mehsud was killed.
"Brick by brick in the last seven weeks we tried to evolve a process by which we could bring peace to Pakistan and what have you (the U.S.) done?" he was quoted as having said.
The foreign ministry said it had summoned U.S. ambassador Richard Olson to protest over the drone strike that killed Mehsud and another that hit a day earlier.
The ministry statement also stressed that despite the drone strike the government was "determined to continue with efforts to engage the TTP."
Islamabad routinely condemns drone strikes as a violation of sovereignty, and Prime Minister Nawaz Sharif urged President Barack Obama to end them during White House talks last week, but summoning the ambassador is an unusual step.
Mehsud's death is the third major blow struck against the TTP by the US this year, following the killing of number two Waliur Rehman in a drone strike in May and the capture of another senior lieutenant in Afghanistan last month.
The TTP's supreme shura, or decision-making council, met Saturday to decide who should now lead the network, which emerged in the wake of a deadly 2007 military raid on the radical Red Mosque in Islamabad.
A Taliban commander told AFP the process was being held up because the meeting location keeps moving to avoid the attentions of the U.S. drones that fly overhead almost continuously.
Candidates under consideration to take over from Mehsud include Asmatullah Shaheen Bhittani, the head of the central shura, and Khan Said, alias Sajna, who became number two after Rehman's death in May, according to AFP.
Senior Taliban commander Azam Tariq dismissed media reports that Said had been elected as "speculation", telling AFP a decision would be made "in the next few days".
For the U.S., Mehsud's death will represent a success for the CIA's drone program at a time when it is under intense scrutiny over civilian casualties.
The TTP has risen to become arguably the biggest security threat facing Pakistan. It was behind the 2008 bombing of the Islamabad Marriott hotel and the attempt to kill schoolgirl activist Malala Yousafzai last year.
The TTP also claimed the 2010 Times Square bomb plot after training Pakistani-American Faisal Shahzad.