Syrian rebels battled ISIS group in northern Aleppo province Saturday, a day after the militant force advanced to the outskirts of the city of the same name, a monitor said.
Islamist rebels including the powerful Ahrar al-Sham group were able overnight to recapture a village from ISIS, the Syrian Observatory for Human Rights said.
The Britain-based monitor said clashes were ongoing for control of a second village captured by ISIS on Friday.
The militant advance on Friday brought the group to within 20 kilometres (12 miles) of the frontline between rebel forces and the army in Syria's second city Aleppo, where government forces are stationed in the Sheikh Najjar industrial zone.
It also threatened rebel access to a key road leading to the Turkish border.
Dozens of militant and rebel fighters were killed in Friday's clashes.
The Observatory had no immediate toll for the ISIS-rebel clashes overnight and into Saturday during which the rebels recaptured Tal Soussin and battled to retake Tal Qrah, a second village.
Elsewhere in Aleppo province, the monitor said heavy clashes were underway between regime forces and ISIS in the area around Kweyris military airport, which is held by the army but besieged by militants.
The Observatory said soldiers and pro-regime militiamen were attacking the insurgent group in several villages around the base in a bid to break the siege.
The ISIS advance in Aleppo comes despite a Russian aerial campaign aimed at targeting the group that began on September 30.
Moscow and Damascus say the campaign targets ISIS and other "terrorists," but rebels and their international backers say it has focused more on moderate and Islamist opposition fighters than the militant group.
The Observatory said Saturday that Russian planes had carried out several strikes overnight in Latakia, Hama and Idlib provinces, which have been key targets of their strikes despite limited ISIS presence.
The group reported at least two Russian strikes on Kafr Nabl in northwestern Syria's Idlib province, which is controlled by the Army of Conquest rebel alliance that includes Al-Qaeda affiliate Al-Nusra Front.
It also said Russian strikes in Idlib on Friday had destroyed a base belonging to the Division 13 rebel group that once received US weapons.
It reported additional strikes in the north of coastal Latakia province, a regime stronghold, and in northwest Hama province, in the centre of the country.
Syrian state television also reported that Syrian planes had carried out their own strikes in Hama province on Saturday.
Russia has focused much of its airpower on the area where Latakia, Idlib and Hama provinces meet in an apparent bid to prevent the Army of Conquest alliance from expanding from Idlib into Hama and Latakia.