WASHINGTON: The U.S. drone strike thought to have killed Taliban chief Akhtar ­Mohammad Mansour represents another escalation in U.S. involvement in the war in Afghanistan by trying to cripple an insurgent group that has for years found refuge on Pakistani soil, Washington Post said in a report on Monday.

The strike early Saturday marks the most aggressive U.S. military action in Pakistan since the 2011 raid that killed Osama bin Laden. It is also thought to be the first time that the U.S. military has directly targeted the top leader of the Afghan Taliban, a potentially destabilizing action that could leave the group violently lashing out as it seeks to find a new leader.

“This is an unprecedented move to decapitate the Taliban leadership in its safe haven of Pakistan,” said Bruce Riedel, a South Asia expert at the Brookings Institution. “It exposes Pakistan’s role in promoting and protecting the Taliban, and will provoke a crisis in U.S.-Pakistan relations.”

But unlike the bin Laden raid, which prompted outrage in Pakistan, the reported strike on Mansour provoked a fairly muted reaction Sunday from Pakistani government, even as Afghan officials cheered and described the attack as proof of the Afghan Taliban’s deep presence in Pakistan.

“While further investigations are being carried out, Pakistan wishes to once again state that the drone attack was a violation of its sovereignty,” the country’s Foreign Ministry said in a statement, adding that it was unable to confirm whether Mansour had been killed.

What the apparent blow means for the Taliban remains uncertain. When Mansour took over after the death of longtime leader Mohammad Omar was announced last year, he had already effectively been running the group for two years, said Wahid Mozhda, a former Taliban diplomat who is now a political analyst in Kabul.

Appointing a successor now may be more challenging, with Omar’s eldest son, Mohammad Yaqob, and top deputies Sirajuddin Haqqani and Moulavi Haibatullah Akhunzada likely to be vying for control.

“It is very hard to anticipate who would be Akhtar Mansour’s successor among these three men,” Mozhda said.

Although Mansour, working through proxies, succeeded in quelling several insurrections against his leadership, he was also apparently a man on the run.

Pakistan’s Foreign Ministry also seemed to suggest that Mansour had been looking over his shoulder. The statement said officials had recovered the body of a man named Wali Muhammad, believed to be Mansour’s alias. That man had been in Iran and only entered Pakistan on Saturday, the day of the drone strike.

“His passport was bearing a valid Iranian visa,” the statement said.

For Taliban leaders, a key question is whether Saturday’s drone strike will be followed up by additional U.S. military actions in southwestern Pakistan.

Afghan President Ashraf Ghani was in Qatar for a two-day state summit. But Ghani’s spokesman described the strike as a potential turning point in the 14½ -year-old Afghanistan conflict.

“This shows the strong U.S. resolve in fighting those who are against peace and are terrorists,” said Dawa Khan Mina Pal, the spokesman.