A drone strike near Daesh's de facto Syrian capital Raqqa killed a terrorist commander heading to Aleppo province on orders from the organization's chief, a monitoring group said Thursday.
His death is the latest in a series of blows to the terrorist group in recent weeks, and comes days after Russian-backed Assad forces recaptured the ancient city of Palmyra from its grip.
Abu al-Hija, a high-ranking Tunisian Daesh commander, was killed late on Wednesday in a strike by a drone that was "most likely operated by the US-led coalition", the Syrian Observatory for Human Rights said.
He had travelled to Syria from Iraq just 24 hours earlier at the behest of Daesh chief Abu Bakr al-Baghdadi, the Britain-based monitoring group said.
Abu al-Hija is the latest senior Daesh member to be killed in recent weeks.
Last week, US forces killed Daesh deputy leader Abd ar-Rahman Mustafa al-Qaduli. Earlier this month one of the group's most notorious commanders, Omar al-Shishani, also died.
"Daesh's leadership is being debilitated," Observatory director Rami Abdel Rahman told AFP.
"Without infiltration of Daesh, these killings would not have been possible."The recapture of Palmyra, known as the "Pearl of the Desert" for its colonnaded alleyways and stunning temples, was seen as the biggest blow so far in the war against Daesh in Syria.
While Russia and the United States back opposing sides in the conflict between the Assad regime and the opposition, both are intent on crushing the terrorists.
"It is clear that Russia and the United States are coordinating in the fight against Daesh," Abdel Rahman said.
Abu al-Hija had been ordered by Baghdadi to travel from Iraq to Aleppo province near Turkey's border, to oversee Daesh resistance to an offensive by US-backed fighters of the Kurdish-led YPG.
"The fighting, which has been especially fierce in the past four or five days, could lead to Daesh being expelled from the area and pushed eastwards into Raqa province," Abdel Rahman said.
A top Pentagon official said earlier this week that Daesh was losing the fight against the US-led coalition in both Syria and Iraq, even as it continues to mount attacks overseas, like the suicide bombings that killed 35 people in Brussels on March 22.