Pictures of the leader of the Afghan Taliban, Mullah Akhtar Mohammad Mansoor (left) who who succeeded Mullah Mohammad Omar.

Pakistan accused the United States on Sunday of violating its sovereignty with a drone strike against the leader of the Afghan Taliban, in perhaps the most high-profile US incursion into Pakistani territory since the 2011 raid to kill Osama bin Laden.

Pakistan protested on Sunday, saying the US government did not inform Prime Minister Nawaz Sharif beforehand.

“This is a violation of Pakistan’s sovereignty,” Sharif told reporters in London, saying it was still unclear who was killed.

Afghanistan said the attack killed Mullah Akhtar Mansoor, which, if confirmed, could trigger a succession battle within the armed group that has proved resilient despite a decade and a half of US military deployments to Afghanistan.

The Afghan Taliban’s leadership council met on Sunday to start considering succession, two Taliban sources told Reuters, in the strongest sign yet the insurgency had accepted he was dead.

The Taliban have not yet officially confirmed that Mansour was killed and there were conflicting accounts on Sunday, with the Afghan government declaring him dead, while Washington stopped just short of doing so.

“At this point, we’re not quite prepared to confirm that he was killed, though it appears likely,” US Homeland Security Secretary Jeh Johnson told “Fox News Sunday.”

The Taliban sources said that Sunday’s meeting of the Rahbari Shura, or leadership council, included discussion of possible successors, including guerrilla commander Sirajuddin Haqqani.

Haqqani, who has a $5 million US bounty on his head, would likely prove an even more implacable foe of Afghan government forces and their U.S. allies.

He is widely seen by US and Afghan officials as the most dangerous warlord in the Taliban insurgency, responsible for the most bloody attacks, including one last month in Kabul in which 64 people were killed.

“Based purely on matters of hierarchy, (Haqqani) would be the favorite to succeed Mansour,” said Michael Kugelman, a senior associate at the Woodrow Wilson Institute think tank.

The Taliban were also considering Mullah Mohammad Yaqoob, the son of Taliban founder Mullah Mohammad Omar, a potential unifier because of his father’s name. Former Guantanamo detainee Mullah Abdul Qayyum Zakir and Mullah Sherin were also cited, the sources said.

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