A senior Islamic State (Isis) leader, Wa'il Adil Hasan Salman al-Fayad, has been killed in United States-led coalition airstrikes in Syria, the Pentagon said on Friday. Wa'il was killed shortly after another strike killed the militant group's top strategist and spokesperson.

Wa'il, who was also known as Dr Wa'il, was killed in a precision strike on Sept. 7 near Raqa, the de facto capital of Isis in Syria, Pentagon spokesman Peter Cook said.

"Wa'il oversaw ISIL's production of terrorist propaganda videos showing torture and executions," said Cook, while calling Wa'il "one of ISIL's most senior leaders".

Earlier, the Pentagon had also announced the killing of Isis spokesman and strategist Abu Mohamed al-Adnani on August 30. Adnani was a close associate of Wa'il.

Cook highlighted that the US officials "will continue to work with our coalition partners to build momentum" in the campaign to eradicate Isis.

The Pentagon also added that it has deployed several US Special Operations Forces to Syria's border with Turkey to battle the militant group at Ankara's request.

Adnani was the main spokesperson for the Islamic State group and played a crucial role in carrying out some of the most high-profile attacks. Those attacks included the ones in Paris, Brussels airport and metro blasts, Istanbul airport attack and also the Dhaka cafe attack in Bangladesh, according to officials.

Last month, Russia had also claimed that a Russian Su-34 bomber in Aleppo killed Adnani along with around 40 other Syrian rebels.