Syrian forces made advances on Sunday against rebels in Hama and latakia provinces as they pressed a ground operation backed by Russian air support.
Washington said the United States and Russia had made “progress” in discussions designed to avoid accidents between them in Syria’s increasingly crowded airspace.
In the northern province of Aleppo, meanwhile, rebels battled to reverse an advance by the ISIS group that brought the jehadis to within a few kilometres (miles) of Syria’s second city.
In Hama, with Russian air support and that of militias on the ground, regime forces captured several areas.
They seized Atshan village from opposition fighters, including Al-Qaeda affiliate Al-Nusra Front, State television and the Syrian Observatory for Human Rights said.
The Observatory, a Britain-based monitor, reported heavy fighting around Atshan as they sought to push northwest and take a neighbouring hilltop.
With support from Russian air strikes, they appeared to be targeting Khan Sheikhun, just across the provincial border in Idlib on a highway connecting Aleppo and Damascus.
The road is cut by rebels in several places north of Khan Sheikhun, and a military source said they had taken the Sukayk hills overlooking the road.
Hama province has been a key target for Russian air strikes that began on September 30, along with parts of the neighbouring provinces of latakia and Idlib.
The strikes appear intended to prevent any advance by the Army of Conquest alliance, which includes Al-Nusra, that holds Idlib and has sought to push into Hama and latakia.
The Observatory said there was heavy fighting in northwestern latakia, and that Government forces were advancing.
In Moscow, Russia’s Defence MSinistry said its forces had hit 55 ISIS targets in the past 24 hours.
The strikes -- in Damascus, Aleppo, Hama, Raqa and Idlib provinces -- destroyed 29 training camps for “terrorists”, 23 defensive positions, two command centres and an ammunition depot.
Meanwhile, the US-led coalition said it carried out five strikes against ISIS in Syria and another 20 in Iraq.
Rebels and their backers say Hama, Idlib and latakia have little or no ISIS presence, and accuse Russia of targeting moderate and Islamist opposition fighters more than the jehadi group.