Mustafa Alou, a commander in the Syrian Democratic Forces (SDF) commando unit, was shot dead late on Monday at his home in the village of Hazima, north of the city of Raqqa, by unknown assailants, local sources told The New Arab’s Arabic-language sister site.

IS was accused of being behind the killing, Al-Araby Al-Jadeed reported.

Alou’s assassination came days after other deadly attacks targeted SDF members and their convoys.

The Kurdish-led, US-backed group spearheaded the fight against IS extremists in 2019 and drove them out of the large swathes of territory they controlled for years in eastern Syria.

But the militant group’s sleeper cells are spread out in the Syrian desert continue to carry out hit-and-run attacks.

At dawn on Tuesday, sources close to Syrian opposition groups told Al-Araby Al-Jadeed that IS militants carried out a large-scale attack on three militant checkpoints belonging to Syrian regime forces and Russian-backed militias.

Two personnel were killed and three others were injured in that attack, which took place in the Raqqa governorate, on a road linking the town of Al-Resafa and the Tabqa Airbase.

Reports said Russian forces have begun bringing in more reinforcements and deploying in different points of the neighbouring Deir Ezzor governorate, where IS activity has increased recently.

Over the weekend, a Russian colonel was killed in a roadside attack blamed on IS in the countryside to the east of Homs.

Oleg Pechevisty had been deployed to Syria months earlier to carry out "special tasks."

Russia has backed Bashar al-Assad's regime for much of a 12-year war that has killed over half a million people and displaced more than half of Syria’s pre-war population.