Pakistan on Sunday accused the United States of violating its sovereignty with a drone strike against the leader of the Afghan Taliban in a remote border area just inside Pakistan.

The president of Afghanistan said the attack killed Mullah Akhtar Mansoor, but a Pakistani passport found at the site bears the name Wali Muhammad and the passport holder was believed to have travelled to Pakistan from Iran on the day of the attack, according to the Pakistani foreign ministry.

Mansoor’s death could trigger a succession battle and deepen fractures that emerged in the insurgent movement after the death of its founder, Mullah Mohammad Omar, was confirmed in 2015, more than two years after it occurred.

The Saturday drone strike, which US officials said was authorised by Barack Obama and included multiple drones, showed the United States was prepared to go after the Taliban leadership in Pakistan, which the government in Kabul has repeatedly accused of sheltering the insurgents.

But Pakistan protested on Sunday, saying the US government had not informed Nawaz Sharif, the prime minister, beforehand.

“This is a violation of Pakistan’s sovereignty,” Sharif told reporters in London.

A US official, speaking on condition of anonymity, acknowledged that Washington had only notified Pakistan after the strike.

Afghan government chief executive Abdullah Abdullah and the country’s top intelligence agency said the attack had been successful.

“Taliban leader Akhtar Mansoor was killed in a drone strike,” Abdullah said in a post on Twitter. “This car was attacked in Dahl Bandin,” he noted, referring to a district in Pakistan’s Baluchistan province just over the border with Afghanistan.

One of the charred bodies at the site has been identified as a local taxi driver but a badly burnt second body has not, according to the Pakistani Foreign Ministry.

The ministry did not directly comment on the possibility that Mansoor had been travelling under another name. Photos of the Wali Muhammad passport found at the site show a passing resemblance to old photos of Mansoor. The ministry said the passport contained a valid Iranian visa.

On Sunday, US homeland security secretary Jeh Johnson said it would be days before Washington could be certain that Mansoor was dead. “At this point, we’re not quite prepared to confirm that he was killed, though it appears likely,” he told Fox News Sunday.

The drone strike underscored the belief among US commanders that under Mansoor’s leadership, the Taliban have grown increasing close to militant groups like al-Qaida, posing a direct threat to US security.

US secretary of state John Kerry said the United States had conducted a precision air strike that targeted Mansoor “in a remote area of the Afghanistan-Pakistan border”.

Mansoor posed a “continuing, imminent threat” to US personnel and Afghans, Kerry told a news conference while on a visit to Myanmar.

“If people want to stand in the way of peace and continue to threaten and kill and blow people up, we have no recourse but to respond, and I think we responded appropriately,” Kerry said.

The Taliban have made no official statement but two Taliban sources said the Rahbari Shura, or leadership council, met on Sunday to begin considering the succession, a move that strongly suggests they accept that he is dead.

They considered Siraj Haqqani, seen by supporters as a strong leader who would defy the US and Afghan governments, and Mullah Omar’s son Mullah Mohammad Yaqoob, a potential unifier because of his father’s name, as well as former Guantánamo detainee Mullah Abdul Qayyum Zakir and Mullah Sherin.

The meeting was expected to continue on Monday and naming a new leader could take days or weeks, the sources said.

“Based purely on matters of hierarchy, [Haqqani] would be the favourite to succeed Mansoor,” said Michael Kugelman, a senior associate at the Woodrow Wilson Institute thinktank.

Efforts to broker talks between the Afghan government and the Taliban had already stalled after a suicide attack in Kabul last month that killed 64 people and prompted President Ashraf Ghani to prioritize military operations over negotiations.

However, Ghani’s office said on Sunday that the removal of Mansoor could open the door to talks and said Taliban members who wanted to end bloodshed should return from “alien soil” and join peace efforts.

Pakistan has in the past denounced US strikes on its soil, calling them a violation of sovereignty, but US officials have said Pakistan has approved some strikes, in particular on militants fighting the Pakistani state.

A Pakistani official in the area said a car had been blown up and two unidentified people had been killed. It was not clear how the vehicle was blown up and the two bodies had been taken to a hospital, said the official, who declined to be identified.

One of the Taliban commanders who dismissed the report of Mansoor’s killing said it had nevertheless spread alarm.

“This rumour has created panic among our followers across Afghanistan and Pakistan,” the senior Taliban member said by phone, adding he was telling his comrades to ignore the report.

In December, Mansoor was reportedly wounded and possibly killed in a shootout at the house of an insurgent leader in Pakistan. The Taliban eventually released an audio recording, purportedly from Mansoor, to dispel the reports.