Besieged by U.S.-backed forces in their last foothold in eastern Syria, Islamic State militants are calling on supporters across the world to stage attacks in their defense, according to a newly released audio recording.

The recording, purportedly from IS, came as the Kurdish-led Syrian Democratic Forces continued to face stiff resistance Tuesday from IS gunmen as U.S.-backed fighters try to push deeper into the village of Baghouz on the eastern bank of the Euphrates River.

The brief, minute-and-a half recording, released by IS supporters on social media and reported by the SITE Intelligence Group late on Monday said that men, women and children in Baghouz are being subjected to a "holocaust by the Crusaders," which is militant jargon for the U.S.-led coalition against IS.

In the audio, an unidentified IS militant calls on Muslim "brothers, in Europe and in the whole world" to "rise against the Crusaders and ... take revenge for your religion." As the man speaks, cracks of gunfire can be heard in the background, apparently meant to suggest that he is in Baghouz.

Read more: ABC News