A US drone strike has killed Hakimullah Mehsud, the head of the Pakistani Taliban, in the North Waziristan region bordering Afghanistan, Pakistani sources have told Al Jazeera.
Security officials said Mehsud and three others were killed on Friday in the Taliban stronghold of Miranshah.
The Pakistani Taliban confirmed Mehsud's killing, and said the group's leadership committee was meeting on Saturday to choose a new leader.
Al Jazeera's Kamal Hyder, reporting from Islamabad, said the killing was expected to have "huge ramifications", not only for the Pakistani Taliban but also for the tentative dialogue process involving the government and the Tehreek-e-Taliban Pakistan (TTP).
"For the TTP, the power struggle may prove to be a real challenge, because they have lost some of their senior commanders," our correspondent said.
Officials said Mehsud was killed after attending a gathering of 25 Taliban leaders gathering to discuss the government's offer of talks.
His funeral was expected to take place on Saturday in Miranshah.
Mehsud's bodyguard and driver were also among the dead, security officials told Reuters news agency.
"Among the dead, who are in large numbers, are Hakimullah's personal bodyguard Tariq Mehsud and his driver Abdullah Mehsud, two of his closest people," said one intelligence source.
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Drones fired four missiles at a compound in Danda Darpa Khel, a village about five kilometres from North Waziristan's capital, Miranshah, other sources said.
The region is one of seven semi-autonomous tribal regions along the Afghan border, which Washington considers to be a major hub of Taliban and al-Qaeda-linked groups plotting attacks on the West and in Afghanistan.
The government issued its usual statement denouncing the drone strike, but did not comment on reports of Mehsud's death.
Chaudhry Nisar Ali, the country's interior minister, said that he could not confirm the death of Mehsud. Imran Khan, the leader of the opposition Pakistan Tehreek-e-Insaf party, condemned the attack as being part of an effort to "sabotage" a potential dialogue process.
As leader of the Pakistani Taliban, Mehsud was the most wanted man in Pakistan and the US had a $5m bounty on his head. He was believed to be in his mid-30s.
He is believed to have been behind a deadly suicide attack at a CIA base in Afghanistan, a failed car bombing in New York's Times Square and other brazen assaults in Pakistan that killed thousands of civilians and security forces.
Mehsud, who had been reported dead several times before, became the leader of the Pakistani Taliban in August 2009 after a drone strike killed Baitullah Mehsud, the group's previous leader and Hakimullah's mentor.
The Pakistani Taliban acts as an umbrella for various jihadist groups who are separate from but allied to the Afghan Taliban.
His death is the latest in a series of setbacks for the Pakistani Taliban.
In May, a drone strike killed Mehsud's second-in-command, and one of his most trusted lieutenants was captured in Afghanistan last month.
The death also follows months of debate over potential peace talks between the Taliban and the new government of Prime Minister Nawaz Sharif, who won a landslide election victory in May, promising to quash the insurgency.
The Pakistani Defence Ministry on Wednesday said 317 US drone strikes in the country's tribal areas had killed 67 civilians and 2,160 fighters in Pakistan since 2008. Other organisations have given much higher estimates for the civilian casualties of drone strikes in the region.
Source: Al Jazeera and agencies