ISLAMABAD, Pakistan — Pakistani security forces were on high alert Saturday amid concerns of revenge attacks after the killing of Pakistani Taliban leader Hakimullah Mehsud in a U.S. drone missile strike.

Mehsud has been reported killed in the past by U.S. and Pakistani security forces _ only to reappear alive. But on Saturday, the Taliban confirmed his killing Friday in the Miranshah area of lawless North Waziristan near the Afghan border.

“We believe that hundreds of thousands more mujahedeen will rise from the drops of Hakimullah’s blood,” Maulana Azam Tariq, a Pakistani Taliban spokesman from South Waziristan, said by phone from an undisclosed location. “The enemy should not be happy with Hakimullah’s martyrdom. We will take revenge with America and its associates.”

Pakistan security forces have been beefed up and placed on high alert across the country, especially in the volatile northwest. Blockades were set up at major entry access roads into Peshawar and additional security deployed around the city’s U.S. consulate.

Mehsud’s funeral was reportedly held in secret Saturday so those attending wouldn’t be targeted by further drone strikes. Miranshah residents reported seeing angry locals fire at several drones overhead.

“Hakimullah has been buried in an undisclosed location in Miranshah,” said another Taliban official, who requested anonymity. It wasn’t possible to bury him in his South Waziristan hometown given the Pakistani army’s control over that area, he added.

“We would definitely take revenge on his death, but the appointment of a new chief is the most important thing right now,” he said.

Friday’s killing was a victory, at least in the short-term, for Washington at a time when its drone program is under growing criticism for mistakenly killing civilians, fueling public anger in Pakistan and helping Taliban recruiting efforts.

Mehsud, on whom the FBI placed a $5 million bounty, has been deemed responsible for planning the failed Times Square bombing in May 2010 and an attack on a CIA base in Afghanistan in 2009 in which seven of the agency’s operatives were killed.

His Pakistani Taliban, related but distinct from its Afghan counterpart, has killed thousands of people in suicide attacks in Pakistan in its bid to replace the nation’s government with an Islamist state.

Despite losing its leader, the decentralized group is viewed as resilient and is expected to regroup relatively quickly. The killing could also damage already strained relations between Washington and Islamabad, which views U.S. drone strikes as a violation of its sovereignty.

“This drone strike is a great setback,” Interior Minister Chaudhry Nisar told reporters in the capital Saturday. “It is not the murder of a person, it is the murder of the peace process.”

He added that Pakistan would formally notify Washington of its displeasure. “The entire range of U.S.-Pakistan relations and cooperation will be reviewed.”

Imran Khan, head of the ruling party of northern Khyber-Pakhtunkhwa province, said his party would introduce a resolution in parliament to block vital NATO truck convoys used to supply the U.S.-led Afghan war.

Mehsud had reportedly just gotten into his vehicle after attending a strategy meeting with other militants at a small mosque when the missiles hit. Also reportedly killed in the attack were his driver, his uncle and two guards.

The biggest loss for the Taliban may be Mehsud’s political skills amid reports of growing tension among the umbrella organization’s 30 or so groups, whether over tactics, recent setbacks or the spoils earned from kidnappings and extortion.

“Hakimullah headed the Taliban operations in different tribal agencies and knew most of the commanders in those areas personally,” said retired Brig. Gen. Mahmood Shah, a security and defense analyst. “His death may be a blow to peace talks but it is also quite a blow to the Taliban itself.”

His death comes after the recent capture of senior commander Latif Mehsud in Afghanistan. And the group’s second in command, Wali-ur-Rehman, was killed in a drone strike in May.

A month later, the group killed 10 mountain climbers in what it said was retaliation for Rehman’s killing. At the same time, the continuing attrition has raised speculation that a weakened Taliban could find itself under pressure to enter talks with the government.

“The Taliban doesn’t have too many options,” said Mushtaq Yusufzai, a Peshawar-based journalist and analyst. “They don’t have an area under their control where they can live without fear of death. The organization needs a break and a place and it is only possible through peace talks, although they are in a state of shock and anger at present.”

Candidates who reportedly might replace Mehsud include ruthless Swat Valley commander Maulana Fazlullah, nicknamed the “Radio Mullah” for his fiery broadcasts, whose men shot and wounded schoolgirl Malala Yousafzai last year; Mehsud’s cousin, Qari Walayat Mehsud, who narrowly escaped Friday’s strike; Maulvi Omar Khalid Khurasani, a top commander; Hafiz Saeed Khan, a South Waziristan cleric and chief; and Khan Said, alias Sajna, a South Waziristan leader credited with masterminding a 2012 jailbreak that freed 400 inmates.

Mehsud, believed to be 33 years old, had maintained a low profile recently, increasingly concerned about drone attacks.

Brought into the insurgency by his cousin Qari Hussain, a top trainer of suicide bombers until he was killed in a drone strike, Mehsud lacked formal education or religious training, but was a popular figure known for his strategic planning, showmanship, emotional outbursts and visceral hate of both the U.S. and Pakistani governments.

Mehsud took over the Pakistani Taliban in August 2009 after a drone strike killed his predecessor, Baitullah Mehsud. He reportedly had two wives and moved frequently to avoid drone attacks, gaining notice by capturing 300 Pakistani soldiers.

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