Foreign Ministry spokesman Aizaz Ahmed Chaudhry did not explain why the envoy was summoned. A U.S. State Department official confirmed the meeting to CNN but would not disclose details about it.

The State Department official would not discuss U.S. operations in Pakistan but stressed the Pakistan Taliban's 2009 attack on a U.S. base in Afghanistan and claims of responsibility for a failed attempt to bomb Times Square in New York.

The official was not authorized to speak publicly and is not being named by CNN.

Pakistan: Peace talks will go ahead

Pakistani Information Minister Pervez Rasheed insisted that Mehsud's death would not delay proposed peace talks between the government and the Pakistan Taliban, amid concern that anger about the strike might derail the process.

Rasheed condemned the use of drones in Pakistan. "Drones are used for killing, but they will not let the peace process be killed with it," the minister told reporters.

Mehsud, who had a $5 million U.S. bounty on his head for his alleged involvement in the 2009 attack , was killed in a drone strike in northwestern Pakistan on Friday, senior U.S. and Pakistani officials told CNN.

He was buried overnight, though the body was burned beyond recognition, Taliban sources said. The organization was scheduled to meet Saturday to pick a new leader, the sources said.

The Afghan Taliban condemned the drone strike as "cowardly" and "barbaric" in a statement posted on its website Saturday, the SITE intelligence group said. The statement urged the Pakistani government and people to take measures to stop the attacks.

A new leader?

No official announcement has yet been made on who will be the new chief for the Pakistan Taliban. But a number of names have emerged, as different factions and individuals jockey for position.

Saleem Mehsud, a journalist who is close to the Mehsuds and familiar with the Pakistan Taliban, told CNN on Saturday that the central shura, or council, of the Pakistan Taliban has approved Sheheryar Mehsud as its new chief.

Sheheryar Mehsud is from the Jangara area of South Waziristan and belongs to the Shabikheil sub-tribe within the larger Mehsud tribe, he said. That's the same sub-tribe that Baitullah Mehsud, who led the Pakistan Taliban before Hakimullah Mehsud, belonged to.

Sheheryar Mehsud, who's 33 years old, has been involved in fighting in Kashmir and Afghanistan, he said.

Pakistan braces for reprisals

There are fears the killing of Hakimullah Mehsud may spark a surge in violence.

This is in part because the attack in Afghanistan in 2009 -- in which seven U.S. citizens died -- was launched in response to the strike that killed Baitullah Mehsud four months earlier.

The Haqqani Network, designated by the United States as a terrorist organization, vowed to avenge Meshud's death. Spokesman Ahmed Yousaf said the group will launch attacks within a few days.

The network is blamed for more than 1,000 U.S. casualties in Afghanistan.

Security around Peshawar, the capital city of Khyber Pakhtunkhwa province in northwest Pakistan, is being beefed up as police and security brace for reprisal attacks, Home Secretary Akhtar Ali Shah said.

"Since this drone strike, we are waiting for a reaction," he said. "We know the reaction will be strong. We have strengthened security in Peshawar, especially at the entry points in to the city. We have extra security on patrol with sniffer dogs."

Strike hit Taliban stronghold

Three other people were killed in Friday's strike, Pakistani intelligence sources and tribal officials said.

They described the incident as a suspected U.S. drone strike in a remote area of Pakistan's North Waziristan region, a Taliban stronghold bordering Afghanistan and Khyber Pakhtunkhwa province.

One missile hit a compound, and another struck a car nearby, the Pakistani sources said.

This is not the first time Hakimullah Mehsud -- who took the reins of the Pakistan Taliban in 2009 -- has been reported killed after a drone strike. In February 2010, multiple sources said he had died after being hit in a drone strike in Pakistan a month earlier.

But reports that he was alive surfaced in April of that year, and in May 2010 he appeared in a video in which he vowed attacks on major U.S. cities.

The fact that senior Pakistani government officials have commented so quickly on the news of his death this time adds credence to the reports.

Pakistan Taliban claimed Times Square plot

The Pakistan Taliban, which has long been conducting an insurgency against the Pakistani government, claimed responsibility for the December 2009 suicide bombing at the United States' Forward Operating Base Chapman in Khost, Afghanistan. Five CIA officers were among the seven U.S. citizens killed, and a member of Jordanian intelligence also died.

The U.S. Justice Department charged Hakimullah Mehsud in the summer of 2010 for his alleged involvement in the attack, and U.S. officials offered a $5 million reward for information leading to his capture.

The group also claimed responsibility for a failed May 2010 attempt to detonate a car bomb in New York's Times Square. The following September, the U.S. State Department designated the Pakistan Taliban a foreign terrorist organization.

Mehsud took over from Baitullah Mehsud, a fellow clan member, in 2009 after the latter was killed in a U.S. drone strike.

Peace prospects

Hakimullah Mehsud's death could make progress in proposed peace talks between the Pakistani government and Pakistan Taliban more difficult.

A relatively young and charismatic leader, he held together a disparate group with different tribal and other allegiances.

There had reportedly been talks about him being involved in peace talks with Pakistan's government.

His killing may upset some elements within the Pakistan Taliban if they believe that the Pakistani government was involved.

The Pakistan Taliban could also pose an increased security threat if it splinters into smaller groups, which could be harder for security forces to detect.

There has been a series of suicide bombings in the region over the past couple of years.

Source:CNN News International