Pakistan has put its security forces on red alert, after the Pakistani Taliban's leader was killed in a suspected US drone strike.
Hakimullah Mehsud and three others were killed in the North Waziristan region bordering Afghanistan on Friday, Taliban commanders and security officials said.
Sources told Al Jazeera that Khan Said, a trusted lieutenant under Mehsud and previously responsible for operations in South Waziristan, was appointed new leader of the group on Saturday.
Al Jazeera's Imtiaz Tyab, reporting from Islamabad, said authorities were bracing for reprisal attacks by the Tehreek-e-Taliban Pakistan (TTP) following Mehsud's death.
"The Pakistani Taliban hasn't said that they're going to strike back but it would be surprising if they didn't. This is a group which is known for carrying out extraordinary attacks on the civilian populous," he 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.
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Drones on Friday fired four missiles at a compound in Danda Darpa Khel, a village about five kilometres from North Waziristan's capital, Miranshah, officials 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.
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.