The Islamic State has released footage purporting to show weapons from a US airdrop to Kurdish forces that have been intercepted by the militants.
The footage was allegedly shot in Kobani, the northern Syrian city that is being defended against a sustained IS offensive by Kurdish fighters.
It shows IS fighters opening boxes seemingly containing grenades and other weapons.
The video has not yet been verified although it appears to be genuine.
The US military on Sunday began airdropping weapons, ammunition and medical supplies to Kurdish forces defending Kobani against Islamic State militants.
The airdrops were the first of their kind and followed weeks of US and coalition airstrikes in and near Kobani, near the Turkish border.
Sky News Defence Correspondent Alistair Bunkall said: "That is not supposed to happen at all, but it is a danger - it has always been a danger - when the West has tried to arm moderate Syrian opposition in the country."
"One way or the other it (the aid) tends to end up in the wrong hands - either directly like this, because you drop it in the wrong place, or because it is sold on the black market."
C-130 cargo planes made multiple drops of arms and supplies provided by Kurdish authorities in Iraq, the US Central Command said.
The airdrops are intended to enable continued resistance to Islamic State efforts to take full control of Kobani, a strategically important town.
Kurdish forces on the ground reportedly withstood a fierce attack by IS on Tuesday, as they waited for reinforcements to arrive after Turkey sad it would help fighters reach the area from Iraq.
Meanwhile, Britain said Royal Air Force drones will fly intelligence-gathering missions over Syria, in a broadening of UK operations against IS beyond Iraq.
And the UK's most senior police officer has claimed at least five Britons are travelling to Iraq and Syria to join IS every week.
"Five a week doesn't sound much but when you realise there are 50 weeks in a year, 250 more would be 50% more than we think have gone already," Metropolitan Police Commissioner Sir Bernard Hogan-Howe said.
"There may be many more who set out to travel to another country and meandered over to Syria and Iraq in a way that is not always possible to spot when you have failed states and leaky borders."
Another video posted on the internet purportedly showed a woman being stoned to death for alleged adultery, with her elderly father taking part in the stoning.
The Syrian Observatory for Human Rights said the execution took place in August or September in an IS-controlled rural area in the east of the central province of Hama.
