The Pentagon said on Friday that a leader in the Takfiri ISIL group leader in Afghanistan and Pakistan, Hafiz Saeed, was killed last month in an airstrike in Nangarhar province.

The Pentagon said on Friday that a leader in the Takfiri ISIL group leader in Afghanistan and Pakistan, Hafiz Saeed, was killed last month in an airstrike in Nangarhar province.

Saeed was named head of ISIL's "Khorasan province," which includes Afghanistan, Pakistan and parts of neighboring countries, early last year when a group of Pakistani Taliban switched allegiance to the  terrorist group.

Pentagon deputy press secretary Gordon Trowbridge said the strike came while US and Afghan special operations forces carried out counter-ISIL operations in southern Nangarhar province throughout July.

"During this time, US forces conducted an airstrike targeting Hafiz Saeed Khan, the Islamic State in the Levant-Khorasan emir, in Achin district, Nangarhar province July 26, resulting in his death," Trowbridge said.

Saeed "was known to directly participate in attacks against US and coalition forces, and the actions of his network terrorized Afghans, especially in Nangarhar," he added.

Details of the strike were not immediately available, but a US official told the BBC that Saeed was killed by drone.

The death of Saeed represents a major setback for the ISIL group as it tries to establish itself as a serious force in Pakistan and Afghanistan.

Afghan authorities erroneously believed Saeed had been killed in another strike in July 2015, when a US drone targeted dozens of ISIL-linked cadres in restive Nangarhar province, close to the Pakistani border.

That attack came less than six months after another strike in Afghanistan killed Abdul Rauf Khadim, who was thought to be the IS number two in the country.

Some Afghan Taliban members have defected to the Takfiri group, with insurgents apparently adopting the black ISIL flag to rebrand themselves as a more lethal force.