Syrian regime warplanes struck on Thursday ISIS positions west of Raqqa on the southern bank of the Euphrates river and along a highway linking the northern city to Aleppo, regime media said.

“The air force destroyed positions and armored vehicles” in the western Raqqa countryside, about 70 km from the city, the media said.

The Syrian Democratic Forces, an alliance of Kurdish and Arab fighters backed by the US, have separately been pushing into the edges of Raqqa in the first days of their attack to seize ISIS’ de facto capital in Syria.

The SDF has scored a series of victories in the past 18 months, including the recapture of the strategic northern city of Manbij, and has now encircled Raqqa and entered it from the east with the help of air strikes and special forces from the US-led coalition.

Syrian forces have also made gains against ISIS in the east of Aleppo province, bringing them to the provincial border with Raqqa which is largely under SDF control.

On Wednesday, a roadside bomb and regime shelling killed at least 19 people, most of them rebel fighters, in southern Syria’s Daraa province.

The Britain-based Syrian Observatory for Human Rights said an explosive device placed on a road by regime forces detonated as a convoy of rebel fighters passed by.

“After the blast, civilians from nearby came to the scene and the regime shelled the area,” said Observatory director Rami Abdel Rahman.

He said 13 of the dead were from local rebel factions, and at least three others were civilians.

The identities of the remaining fatalities had not been confirmed.

The monitor said the toll in the incident in the northwest of the province could rise further because several people were suffering serious injuries.

Daraa province is one of the last remaining bastions of rebel forces, who retain control of a majority of the region even as they have been routed elsewhere.