In March, a senior commander with Isis (Islamic State) was driving through northern Syria on orders to lead militants in the fighting there when a drone blasted his vehicle to oblivion.
The killing of Abu Hayjaa al-Tunsi, a Tunisian jihadi, sparked a panicked hunt within the group's ranks for spies who could have tipped off the United States-led coalition about his closely guarded movements. By the time it was over, the group would kill 38 of its own members on suspicion of acting as informants.
They were among dozens of Isis members killed by their own leadership in recent months in a vicious purge after a string of airstrikes killed prominent figures. Others have disappeared into prisons and still more have fled, fearing they could be next as the jihadi group turns on itself in the hunt for moles, according to Syrian opposition activists, Kurdish militia commanders, several Iraqi intelligence officials and an informant for the Iraqi Government who worked within Isis ranks.
The fear of informants has fuelled paranoia among the militants' ranks. A mobile phone or internet connection can raise suspicions.
As a warning to others, Isis has displayed the bodies of some suspected spies in public - or used particularly gruesome methods, including reportedly dropping some into a vat of acid.
Isis "commanders don't dare come from Iraq to Syria because they are being liquidated" by airstrikes, said Bebars al-Talawy, an opposition activist in Syria who monitors the jihadi group.
Over the past months, American officials have said that the US has killed a string of top commanders from the group, including its "minister of war" Omar al-Shishani, feared Iraqi militant Shaker Wuhayeb, also known as Abu Wahib, as well as a top finance official known by several names, including Haji Iman, Abu Alaa al-Afari or Abu Ali Al-Anbari.
The purge comes at a time when Isis has lost ground in both Syria and Iraq. An Iraqi Government offensive recaptured the western city of Ramadi from Isis earlier this year, and another mission is underway to retake the nearby city of Fallujah.
Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said some Isis fighters began feeding information to the coalition about targets and movements of the group's officials because they needed money after the extremist group sharply reduced salaries in the wake of coalition and Russian airstrikes on Isis-held oil facilities earlier this year.
The damage and the loss of important Isis-held supply routes into Turkey have reportedly hurt the group's financing.
"They have executed dozens of fighters on charges of giving information to the coalition or putting (GPS) chips in order for the aircraft to strike at a specific area," said Abdurrahman, referring to Isis in Syria.
"Daesh is now concentrating on how to find informers because they have lost commanders that are hard to replace," said a senior Iraqi intelligence official in Baghdad, using the Arabic acronym for the Isis.
In Mosul last month, about a dozen fighters and civilians were drowned in a vat filled with acid, one senior Iraqi intelligence official said.
Sherfan Darwish, of the US-backed Syria Democratic Forces, which has been spearheading the fight against Isis in Syria, said there is panic in Isis-held areas where the extremists have killed people simply for having telecommunications devices in their homes. "There is chaos. Some members and commanders are trying to flee," Darwish said.
The US-led coalition has sought to use its successes in targeting Isis leaders to intimidate others. In late May, warplanes dropped leaflets over Isis-held parts of Syria with the pictures of two senior militants killed previously in airstrikes. "What do these Daesh commanders have in common?" the leaflet read. "They were killed at the hands of the coalition."
The jihadis have responded with their own propaganda. "America, do you think that victory comes by killing a commander or more?" Isis spokesman Abu Mohammed al-Adnani said in a May 21 audio message. "We will not be deterred by your campaigns and you will not be victorious." AP