DAMASCUS, Oct. 21-- The Islamic State (IS) militants captured one of the weapons shipments airdropped by the United States to the Kurdish fighters of the People Protection Units (YPG) in the city of Ayn al-Arab in northern Syria, a monitoring group said Tuesday.

Two weapons shipments airdropped by the U.S. fighters landed at areas under the IS control in the vicinity of Ayn al-Arab, also known as Kabone, and one of them was captured by the IS, said the Syrian Observatory for Human Rights.

The second arms load was likely destroyed by the U.S. war jets after being confirmed to have landed in the wrong area, said the Observatory.

Meanwhile, the IS released a video footage on Tuesday, showing one of its fighters showcasing the captured weapons near Ayn al- Arab. The weapons included grenades and RPG shells.

On Monday, a U.S. aircraft dropped large quantities of weapons, munitions and medical supplies to outgunned Kurdish fighters of the YPG battling the IS in Ayn al-Arab.

Kurdish activists were cited by some Arab television stations on Monday as saying the new weapons supplies could contribute to tilting the balance of power in favor of the Kurds in Ayn al-Arab, but the U.S. Central Command warned that Ayn al-Arab could still fall as the security situation there remains "fragile."

Over the past month, the IS militants armed with heavy weapons have been on a crushing offensive to capture the strategically important Ayn al-Arab on the Syrian-Turkish border.