ISLAMABAD (Reuters) - Pakistan’s interior minister said on Tuesday he could not confirm that Afghan Taliban leader Mullah Akhtar Mansour had been killed in a U.S. drone strike, and described Washington’s justification for the attack as “against international law”.

Newspapers containing news about Afghan Taliban leader Mullah Akhtar Mansour are on display at a stall in Peshawar, Pakistan, May 23, 2016. REUTERS/Fayaz Aziz

U.S. President Barack Obama said on Monday that Mansour had been killed in the drone strike, and the Pentagon said separately that Mansour was plotting attacks that posed “specific, imminent threats” to U.S. troops in Afghanistan.

On Tuesday, Interior Minister Chaudhry Nisar Ali Khan told reporters that the body recovered on Pakistani soil, near the Afghan border, was charred beyond recognition, adding that DNA samples would be tested against a relative who had come forward to claim the body.

“The government of Pakistan cannot announce this without a scientific and legal basis,” Khan told a news briefing.

He did not identify the relative or say whether he or she claimed to be related to the Taliban leader or someone else.

Two U.S. officials told Reuters that U.S. intelligence and military agencies used multiple streams of intelligence, including human intelligence and electronic surveillance to locate and identify the car carrying Mansour.

That enabled multiple drones operated by the Joint Special Operations Command to incinerate the car when it reached an empty stretch of road in a remote area where there was little danger of causing civilian casualties.

“There were multiple forms of intelligence attributed to tracking him down,” a U.S. official said.

Khan rejected the U.S. argument that it could launch attacks across borders in order to protect its interests.

“For the U.S. government to say that whoever is a threat to them will be targeted wherever they are, that is against international law,” he said. “And if every country in the world adopts this rule, it will be the law of the jungle.”

Pakistan and the United States have been uneasy allies in the war against the Taliban and other Islamist militants in the region.

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Critics in Afghanistan and the United States accuse Pakistan of allowing the Afghan Taliban’s leadership to take shelter on its territory, something that Islamabad has denied.

The militant movement has made territorial gains and carried out a series of deadly attacks across Afghanistan since NATO forces officially wound down their combat mission at the end of 2014, undermining the Western-backed government in Kabul.

Recent events echo those in 2011, when U.S. special forces raided a building in the Pakistani city of Abbottabad that killed longtime al Qaeda leader Osama bin Laden, infuriating and severely embarrassing Islamabad.

CROSS-BORDER STRIKE?

Khan said the car was destroyed on Pakistani territory but was fired “from another country”, presumably Afghanistan, where more than 10,000 U.S. and coalition troops remain.

Khan added that Pakistani authorities were also investigating a passport bearing the name of Wali Muhammad, which was found near the burned out shell of the car believed to have been the target of the drone attack.

He confirmed the passport in question had been used to travel from Pakistani airports multiple times, and that it held valid visas for Iran, Dubai and Bahrain.

If the travel document proves to have been used by Mansour himself, it would raise fresh questions about how the Taliban leader was able to move freely in and out of Pakistan and whether he had help from the country’s security apparatus.

Khan on Tuesday disputed that elements of Pakistan’s security apparatus supported the Taliban leadership.

“If (Mansour) was availing Pakistani intelligence agency support and help, would he be travelling like this?,” he asked, referring to reports that the target was alone with a single driver.

The circumstances surrounding the killing remain murky, including how the U.S. verified it was Mansour who was killed in the attack and how any documents could be recovered from the fiery scene.

“You could not see a spot of paint ... that’s how bad it was hit,” Khan said. “How was a passport lying just a few yards away? So first we have to establish that, whether he was actually using it.”

The Taliban have not issued any official statements on Mansour since Saturday’s drone strike.

However, Taliban officials, speaking on condition of anonymity, have said Mansour is dead and a council is meeting to choose a successor, the second such leadership shura in a year after the death of the movement’s founder, Mullah Mohammad Omar, was confirmed in 2015.

MYSTERIOUS PASSPORT

Authorities in Quetta, the Baluchistan capital, showed a copy of the recovered passport, which has a photo bearing a strong likeness to the officially released Taliban picture of Mansour, to a Reuters reporter.

They also noted that it bore an exit stamp from Iran’s land border with Pakistan dated May 21, the day of the drone strike.

Pakistani immigration records show that the Wali Muhammad passport was used at least 18 times since 2006 to travel internationally, two senior officials in the Federal Investigation Agency, which manages borders, told Reuters.

One of the officials in the southwestern province of Baluchistan said the passport was used mostly over the land border with Iran and from the airport in the southern city of Karachi, with the last exit from Karachi en route to Dubai on March 31, 2015.

The second official reviewed computerised records of the passport and said there were “18 travel events” from Karachi airport starting in 2007, with the last arrival at Karachi on April 2, 2015.

A spokesman for the Iranian foreign ministry was quoted on state media denying that such an individual had crossed the border from Iran to Pakistan at the time in question.

Authorities in the United Arab Emirates did not respond to questions on whether Mansour might have entered Dubai using an assumed name or whether there was any record of a Wali Muhammad visiting.