The Islamic State group has been defeated at its final shred of territory of Baghouz in Syria, the U.S.-backed Syrian Democratic Forces (SDF) said on Saturday, announcing the end of its self-declared "caliphate" that once spanned a third of Iraq and Syria.

The SDF declared the "total elimination of (the) so-called caliphate," Mustafa Bali, head of the SDF media office, wrote on Twitter.

"Baghouz has been liberated. The military victory against Daesh has been accomplished," he wrote.