ISLAMABAD - Complicated ties between Pakistan and the United States could be on course to become nasty after the Osama Bin Laden-styled US strike deep inside Pakistan over the weekend to kill Afghan Taliban chief Mullah Akhtar Mansour.

US officials maintained they had no definitive proof of his death in multiple strikes, authorised by President Barack Obama, in the remote Pakistani town of Ahmad Wal in Balochistan.

A statement, issued by Pakistan’s Foreign Office late Sunday, said one of the victims of the attack was a driver named Muhammad Azam while the identity of the second “is being verified”.

But Afghanistan’s main spy agency and the country’s Chief Executive Abdullah Abdullah asserted that Mansour had been killed in the attack.

Afghan Taliban, who until now are largely seen as pro-Pakistan, could turn against Islamabad and react violently by offering assistance to TTP (Tehrik-e-Taliban Pakistan) for staging terrorist activities in the country.

Pakistan therefore reacted sharply by calling the strike an attack on its sovereignty and stressing that only negotiations could bring lasting peace to war-torn Afghanistan.

Security officials said they recovered two bodies charred beyond recognition from a smouldering vehicle in Kochaki area near Pak-Afghan border.

The passenger, who is suspected of being Mansour, was said to be returning from Iran on Saturday and was using a Pakistani passport with the name Muhammad Wali. He had a valid Iranian visa and was travelling on a vehicle hired from a transport company in Taftan.

The driver was a civilian who worked for a rental company, according to the officials, contradicting the US account that he was a “second combatant”.

Unable to confirm Mansour’s death, Pakistan Foreign Office Spokesman Nafees Zakria said: “We are still investigating... At this point we cannot confirm his death.”

He said peace in Afghanistan was possible only through negations. “Taliban must quit violence and come to the negotiation table,” he said, adding, “Military action is not a solution.”

US Secretary of State John Kerry yesterday said both Pakistan and Afghanistan were notified of the airstrike but he declined to elaborate on the timing of the notifications, which he said included a telephone call from him to Prime Minister Nawaz Sharif.

Officials at the foreign ministry said the call was received after the hit “which was tantamount to violating our sovereignty”.

“You can call it a mini-OBL type operation. We knew only when there were claims Mansour had been killed. The telephone call was a mere formality,” said an official.

A statement issued by the foreign ministry did not confirm Mansour’s death and also termed the strike ‘violation’ of Pakistan’s sovereignty. It said the US late Saturday shared information about the drone strike which was shared with the PM and Army Chief “after the drone strike”.

Meanwhile, a senior Taliban source told AFP “I can say with good authority that Mullah Mansour is no more.”

Mansour’s death, which risks igniting new succession battles within the fractious group, was confirmed by two other senior figures who said its top leaders were gathering in Quetta to name their future chief.

The Taliban sources said that Sirajuddin Haqqani, leader of the dreaded Haqqani network and one of Mansour’s deputies, was among the frontrunners, adding that Mullah Abdul Ghani Baradar was also in contention.

It is unclear when Mansour’s successor will be announced. The Taliban have not commented officially on Mansour’s death or the leadership succession.

Pakistan and the US admit their relationship was complicated at the best as the two differ on countering Taliban, and Washington believes Islamabad was playing double-game with them, especially on Afghanistan peace.

Even before claiming to kill the Taliban leader, the US hinted at more aid restrictions after the F-16s deal controversy where the compelling ally asked the ‘complicated’ partner to pay the whole price of the jets instead of a share.

This promoted Prime Minister Nawaz Sharif to push his top diplomats including Sartaj Aziz and Tariq Fatemi to find a way out to warm up the ties.

About the drone strike, former Pakistan ambassador to US, Senator Sherry Rehman, said this was ‘not a small matter’ as Pakistan had been put in the crosshairs of a dangerous regional security crisis. “We demand an urgent explanation from a government that seems to have lost its grip on critical issues of foreign policy,” she said.

The PPP vice president said the government needed to explain what was going on “who issued Mansour’s travel documents and what did Secretary Kerry’s call to the PM signal.” She said her party will raise these questions in the parliament as well.

Sherry pointed out: “We have been told repeatedly by the government that all was going smoothly in the Quadrilateral talks, and that they were facilitating talks with the Taliban with the support of the US, so what was this strike about? Why are they unable to connect the dots in such vital strategic policy matters?”

Defence analyst Lt-Gen Talat Masood (r) reiterated the government must minimise its dependence over US. He feared anti-Pakistan lobby was sabotaging Pak-US ties and convincing Washington to quash defence deals with Islamabad.

Husain Haqani, another former ambassador to the US, predicted strained ties and said it would put Inter-Services Intelligence on alert. “It is also a signal to the ISI that the US is losing patience with promises of Pakistan facilitating talks with the Taliban and is finally willing to strike at the Afghan Taliban leadership in Pakistan,” he said.

Imtiaz Gul, director of Centre for Research and Security Studies said Mansour’s death could be devastating for the Taliban. “First Mullah Omar and now Mansour - once you take the core out of a movement it could begin to unravel,” he commented.

Gul said peacemaking will become even more difficult “if you are dealing with so many leaders. This has been the strategy for several years - to splinter them and make deals - but whether that works, we don’t know.”