Turkey's Prime Minister Binali Yildirim said Sunday that his nation's forces and Syrian rebels expelled the Islamic State group from the last areas of the Syrian-Turkish border under its control.

"From Azaz to Jarabulus, our 91 km border has been completely secured. All terrorist organisations have been repulsed and they have gone," Yildirim said during a televised speech while visiting the southeastern city of Diyarbakir.

The Syrian Observatory for Human Rights said earlier that IS lost its last stretch after the few remaining villages it controlled were recaptured by rebels.

The Britain-based monitor said "rebels and Islamist factions backed by Turkish tanks and warplanes" had taken several villages on the border "after IS withdrew from them, ending IS's presence... on the border."

The loss of the Turkish border will deprive IS of a key transit point for recruits and supplies, though the group continues to hold territory in both Syria and Iraq.

The advance comes after Turkey launched an operation on on August 24 dubbed Euphrates Shield, saying it was targeting both IS but also Syrian Kurdish forces that have been key to driving the jihadists out of other parts of the Syrian-Turkish border.

The Kurdish YPG militia is a key partner of the US-led coalition against IS, and has recaptured large swathes of territory in Syria from the extremist group.

But Ankara considers the YPG a "terrorist" group and has been alarmed by its expansion along the border, fearing the creation of a contiguous, semi-autonomous Kurdish region in northern Syria.

Turkey also says the YPG is a sister organisation of the separatist Kurdistan Workers' Party (PKK) with whom a two-year ceasefire collapsed last year.

The PKK -- proscribed by Ankara and its Western allies as a terrorist organisation -- has since launched frequent attacks on security forces in the country's southeast.

Yildirim said that Turkey's purpose in northern Syria was to "cleanse Daesh (IS), PKK, YPG, PYD elements" and to secure its border.