Idlib is the last significant rebel-held area in Syria, and since December has come under a renewed offensive by regime troops supported by their Russian and Iranian allies.
The worsening situation at makeshift camps in Idlib province comes as Russian-led airstrikes saw at least 18 people killed on Tuesday.
The unnamed informant's family reportedly suffered under Islamic State rule prompting him to seek revenge, General Mazloum Abdi said.
Regime airstrikes have pounded Syria's Idlib province, with clashes reported between government and rebel ground forces.
About 300 fighters are believed to remain in the devastated Syrian village of Baghouz.
Russia's alliance with Turkey is being tested by the ongoing presence of militant groups in Idlib and attacks on Syrian Kurds in the north.
The deals may be in jeopardy after local challenges emerged to two precarious international arrangements designed to avoid new violence.
The deputy director of Russia's state-run Concern Radio-Electronic Technologies said Moscow would soon be able to track planes, "be it in Israel or Saudi Arabia or even in Europe."
While the president criticized Russia and Iran during the Security Council meeting, he expressed appreciation for the "restraint" both nations have shown in Syria's Idlib province.
A deal struck Monday by Russia and Turkey appears to have stalled any sort of imminent Syrian military attack on Idlib, but tensions remain high in the region.
Syrian air defenses are reportedly engaging missiles over the west coast city of Latakia.
Vladimir Putin and Recep Tayyip Erdogan agreed to establish a demilitarized zone of 15 to 20 kilometers in Idlib.
"What happened and continues to happen in Raqqa is a humanitarian catastrophe," Russian Foreign Minister Sergey Lavrov said.
U.S. Special Ops photos featured a French military vehicle in Syria's Deir Ezzor, but they were quickly pulled from social media.
The U.S. has already entered talks with France and the U.K. in what Russia fears could be a new set of strikes against its Syrian ally.
The U.N. has warned an Idlib offensive could cause the worst humanitarian catastrophe of the 21st century.
Up to 2 million civilians and opposition fighters await a Syrian military assault on the Islamist-held province of Idlib, a move championed by Russia and criticized by the West.
There are increased fears that Russia, Syria and Iran are plotting an assault on the last major rebel stronghold in Syria, Idlib, where many civilians still live.
Syrian President Bashar al-Assad said in July that regaining control of Idlib was a priority.
After ISIS was mostly defeated in the east, the Syrian military set its sights on rebel-held Idlib, while Turkey targeted U.S.-backed Kurds in Afrin, Aleppo.
"The U.S. must step back from this grave mistake and not allow itself to be blackmailed by the terrorist outfit," Turkey's top diplomat said.
A year after winning Aleppo, the Syrian military and its Russian ally launched a devastating offensive against the last rebel province of Idlib.
Russia used electronic and conventional warfare to take down a baker's dozen drones.
Russian and U.S. allies are battling insurgents and jihadists trying to topple the Syrian government, but the latter wants to reshape the nation.
As Russia and Turkey increasingly cooperate in Syria, a lucrative natural gas pipeline deal progresses.
Though inspectors tried to remove Syria's chemical arsenal in 2014, evidence of sarin use in a recent strike suggests some remained.