US backed Kurdish group seize key village from IS militants in Syria

US-backed Syrian fighters seized a key village on Tuesday from the Islamic State group, further chipping away at their last eastern holdout on the Iraqi border, a Britain-based monitor said.

Backed by air strikes of the US-led coalition, the Syrian Democratic Forces have since September been battling to expel the hardline militants from the so-called Hajin pocket in the eastern province of Deir Ezzor.

In recent weeks, they have whittled it down to just a handful of villages on the eastern banks of the Euphrates River.

On Tuesday, the Kurdish-led alliance seized the largest of these from IS militants after they fled, the Syrian Observatory for Human Rights monitoring group said.

"The SDF took control of Sousa after the withdrawal of IS fighters to territory that remains under their control," Observatory chief Rami Abdel Rahman said.

That leaves IS battling to defend just 15 square kilometres (under six square miles) of land, he added.

IS overran large parts of Syria and neighbouring Iraq in 2014, proclaiming a "caliphate" in areas under their control.

But they have since lost most of that to various offensives in both countries -- even if they retain a presence in Syria's vast Badia desert, where Russia-backed regime forces have fought them.

According to the Observatory, more than 1,100 IS militants have been killed since the start of the operation on September 10, while more than 600 SDF fighters have also lost their lives.

Around 360 civilians including 130 children have also been killed, the monitor says.

Syria's war has killed more than 360,000 people and displaced millions since it started in 2011 with the brutal repression of anti-government demonstrations.