IS 'caliphate' in Syria will be defeated within a month: commander

"The operation of our forces against IS in its last pocket has reached its end and IS fighters are now surrounded in one area," Mazloum Kobani, the chief of the Kurdish-led Syrian Democratic Forces, told AFP.

With backing from the US-led coalition, the SDF are in the last phase of an operation started on September 10 to defeat the jihadists in the Euphrates Valley in eastern Syria.

"We need a month to eliminate IS remnants still in the area," said Kobani, who spoke to AFP on Thursday near the northeastern Syrian city of Hasakeh.

A few hundred IS fighters are defending a handful of hamlets near the Iraqi border, the last rump of a "caliphate" which the jihadist organisation proclaimed in 2014 and once covered territory the size of Britain.

"I believe that during the next month we will officially announce the end of the military presence on the ground of the so-called caliphate," Kobani said.

Intense fighting in the area known as "the Hajin pocket" has left hundreds of fighters dead on both sides, according to the Syrian Observatory for Human Rights war monitor.

IS lost the town of Hajin late last year and the subsequent collapse of its defences saw the Kurdish-led SDF conquer one village after another.

Kobani said their battle had been complicated by the jihadist group's shifting strategy after the fall of their de-facto Syrian capital of Raqa in 2017.

New tactics include "sleeper cells everywhere, secretly recruiting people again, and carrying out suicide operations, bombings, and assassinations", he said.

"We expect there will be an increase in the intensity of IS operations against our forces after the end of their military presence," Kobani said.

IS has retained a presence in Syria's vast Badia desert and has claimed a series of attacks in SDF-held territory.