Islamic State group fighters seized at least one air drop of weapons airdropped by US -led coalition forces intended for Kurdish militiamen battling the extremist jihadis, according to a propaganda video posted online.
Hand grenades, ammunition and rocket-propelled grenade launchers, can be seen in the video uploaded by a media group loyal to the Islamic State group, which appeared at first impressions to be authentic.
On Tuesday, IS loyalists on social media posted sarcastic thank you notes to the United States, including one image that said "Team USA."
The British-based Syrian Observatory for Human Rights, which bases its information on a network of activists on the ground, said the militants had seized at least one cache of weapons intended for their enemies.
The caches were airdropped early on Monday to Kurds in the embattled Syrian town of Kobani that lies near the Turkish border.
The militant group has been trying to seize the town for over a month now, causing the exodus of some 200,000 people from the area into Turkey.
IS militants already possess millions of dollars-worth of US weaponry that they captured from fleeing Iraqi soldiers when the group seized swaths of Iraq in a sudden sweep in June.
State Department deputy spokeswoman Marie Harf said the US couldn't confirm its accuracy and was seeking more information.
This week, a British-based anti-extremism thinktank alleged that "half" of all donations made to minor Syria-based charities end up in the hands of IS, who were formerly known as ISIS.
Haris Rafaq, of the Quilliam Foundation told Newsweek Europe: “When you take out the major charities like the British Red Cross and the Red Crescent, more than half of the ‘aid’ that goes out to Syria ends up with militant groups”. The majority of this money comes from the UK and goes to ISIS.
“ISIS are the biggest beast in the region, so they can have their pick of resources on the ground,” Rafiq added.
On Tuesday, the US Central Command said its forces conducted four airstrikes near Kobani that destroyed IS fighting positions, an IS building and a large IS unit.
Also on Tuesday, Syrian government airstrikes hit a rebel-held town along the country's southern border with Jordan, killing at least eight people.
Activists with the Local Coordination Committees and the Observatory said the number of those killed was likely to rise as there are more victims under the rubble.
The LCC said Syrian government planes dropped crude explosives-laden canisters on the town of Nasib on the Syria-Jordan border.
The airstrikes are part of battles between Syrian government forces and Islamic rebel groups for control of the area.
Syrian government forces have been heavily bombing rebel areas in recent weeks, while the U.S-led coalition has been conducting airstrikes against Islamic State militants elsewhere in Syria.