BEIRUT (AFP) - A US military airdrop of weapons meant for Kurdish fighters fell into the hands of their extremist foes near the Syrian battleground town of Kobane, a monitor said on Tuesday.

The US Air Force parachuted crates of weapons, ammunition and medical supplies on Sunday night to resupply Kurds defending the Syrian town of Kobane from ISIS (Islamic State in Iraq and Syria) militants.

"One load was taken by (ISIS) and there are contradictory reports about a second" which was also reported to have gone astray, said the Syrian Observatory for Human Rights.

Some sources said two consignments had landed in the hands of ISIS, but others said that warplanes from a US-led coalition destroyed one of them once the error was detected.

But US Central Command, which oversees American forces in the Middle East, said Monday that only one of 27 bundles had gone astray and that American warplanes bombed it to prevent it being snatched by ISIS.

In a video posted on the Internet, titled "Arms and ammunition dropped by US planes in an IS-held area of Kobane", using another acronym for ISIS, a masked gunman shows off what appears to be one such bundle attached to a parachute.

"This is the American aid thrown to the infidels," he says, opening wooden boxes filled with rockets and grenades, as aircraft could be heard circling overhead.

"Praise be to God, this is booty for the mujahedeen (Islamic warriors)."