The U.S. drone strike that killed the head of the Pakistani Taliban drew expressions of outrage from political officials here Saturday, capped by a public rebuke of the Obama administration.

A day after three missiles were fired into a vehicle in northwestern Pakistan, senior Pakistani Taliban members confirmed Saturday that Hakimullah Mehsud and four others had been killed in the attack, a major victory in the decade-old U.S. campaign targeting Islamist militants. But after they had buried their former chief, Pakistani Taliban leaders began to regroup, vowing retaliatory strikes against U.S. interests.

With security heightened across Pakistan, the sharpest effect so far has been the derailment, at least temporarily, of Prime Minister Nawaz Sharif’s efforts to engage Mehsud and other Taliban leaders in peace talks. In an angry, hour-long, televised news conference Saturday, Interior Minister Chaudhry Nisar Ali Khan accused the United States of “ambushing” the Sharif government’s efforts by authorizing the strike.

“The government of Pakistan does not see the drone attack as an attack on an individual, but as an attack on the peace process,” he said.

After Khan spoke, Pakistan’s Foreign Ministry lodged a formal protest with U.S. Ambassador Richard G. Olson, saying the attack had violated Pakistan’s sovereignty. The Foreign Ministry also plans to protest to the five permanent members of the U.N. Security Council.

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When Sharif returns here after spending the weekend in London, he and his national security team will reexamine “the entire perspective” of future relations with the United States, including NATO’s use of Pakistani highways to transport equipment to and from Afghanistan, Khan said.

U.S. officials had no immediate comment Saturday, although a White House official noted Friday that Mehsud was linked to a 2010 plot to bomb Times Square in New York.

Mehsud, who Taliban leaders said was buried early Saturday in North Waziristan, was also implicated in a 2009 attack on a CIA outpost in eastern Afghanistan that killed seven Americans. The United States posted a $5 million bounty for him, as well as for another senior Pakistani Taliban leader, Wali ur-Rehman, who was killed in a drone strike in May.

Several analysts said those killings represent a major setback for the militant group, which is composed of dozens of factions and is loosely affiliated with al-Qaeda, as well as with the Afghan Taliban.

But Pakistani Taliban leaders met Saturday to try to select a new leader and shake off suggestions that Mehsud’s death will have a lasting impact on the group.

Some Taliban officials said that Khan Said, the group’s second-in-command, has emerged as a front-runner to succeed Mehsud. But two Taliban members who spoke on the condition of anonymity said the group has decided to appoint Sheheryar Mehsud, a little-known 33-year-old militant who has fought in both Kashmir and Afghanistan, as its temporary leader.

Other officials said that a final decision could come as early as Sunday.

Saifullah Mehsud of the Islamabad-based FATA Research Center, which investigates terrorism organizations, said that whoever is chosen is likely to be less rigid than Hakimullah Mehsud, who was controversial even among Taliban sympathizers for authorizing attacks on civilians.

“The first reaction [from the Pakistani Taliban] is going to be one of retaliation, and they will want revenge, and they may call off the peace talks, but in the long run, having a figure like him not being around is going to make it easier for all parties involved,” Saifullah Mehsud said.

Several Pakistani cities, including the capital, Islamabad, were on high alert Saturday, and an Interior Ministry official said additional precautions were being taken around diplomatic compounds.

“Every drop of Hakimullah’s blood will turn into a suicide bomber,” Azam Tariq, a local Taliban spokesman, told reporters in South Waziristan.

Khan, the interior minister, blamed the United States for Pakistan’s security problems, saying that the drone campaign is fueling instability in the country. He said Sharif had asked Obama during a White House meeting last month for assurances that the United States would not interfere in the planned talks with the Taliban.

“Is this how you support the dialogue?” Khan said. “One day before discussions are supposed to start, you take out the leader who was supposed to talk?”

Also expressing outrage, the chief political leader of the northwestern province of Khyber Pakhtunkhwa said Saturday that he will immediately press for a blockade of NATO supply routes through Pakistan.

“We will not allow it. Even if our government falls, then let it be so,” said Imran Khan, the leader of the Movement for Justice party, which heads the local government in Khyber Pakhtunkhwa, a main route for NATO convoys to and from Afghanistan.

But Zahid Hussain, a military analyst based in Islamabad, said that much of Pakistan’s military and political establishment is privately “quite happy” that the country’s “No. 1 most-wanted man” is dead. Neither the military nor the powerful intelligence service commented on Hakimullah Mehsud’s death Saturday.

“They knew the peace talks were never going to go anywhere,” Hussain said.

Haq Nawaz Khan, Shaiq Hussain and Saleem Mehsud contributed to this report.