Daish rebels attacked Syrian government forces and their allies in countryside east of Homs and Hama on Wednesday, the Syrian Observatory for Human Rights said.
Heavy fighting raged around the mountainous Jabal Al Shomariya area in Homs province, and the government side was carrying out air strikes there, the British-based monitoring group said.
Pro-Damascus media outlets quoted a military source saying warplanes had hit targets in the eastern Hama countryside, which borders Jabal Al Shomariya to the north.
Daish has been losing ground to government forces further east, close to its stronghold of Deir Al Zor province and Al Sukhna, the last town it holds in Homs province.
Several sides in Syria’s crowded battlefield are fighting Daish, including Syrian government forces backed by Russia and Iran, and US-backed, Kurdish-dominated forces around its Raqqa stronghold.
Separately, buses carrying Syrians left refugee camps in a Lebanese border area bound for a rebel-held part of Syria on Wednesday under a truce deal between Hezbollah and Al Nusra Front militants, a security source and Hezbollah TV said.
Thousands of Syrians including militants and their families and refugees are to leave the border zone of Jroud Arsal and head for Syria’s northwestern Idlib province under the deal.
The transfer echoes deals struck within Syria in which Damascus has shuttled rebels and civilians to Idlib and other opposition areas. Such evacuations have helped President Bashar Al Assad recapture several rebel bastions over the past year.
The ceasefire took effect last week, just days after Hezbollah and the Syrian army launched an offensive to drive Nusra Front and militants from their last foothold along the Syria-Lebanon border.
The Jroud Arsal operation has highlighted the major role of Hezbollah in fighting militants along the frontier during Syria’s six-year war, sending thousands of combatants to support Assad’s government.
Hezbollah’s Al Manar television said that 26 buses had crossed from the Arsal area to Wadi Hmeid further northeast in the direction of the Syrian frontier. A security source said they were carrying 1,020 people.
Nearly 7,000 Syrians are expected to leave the area under the ceasefire deal, according to Hezbollah-run media outlets.
Security sources say that some 1,000 Nusra Front militants are among those who will leave the area for Idlib aboard dozens of buses.
The deal included the release of several Hezbollah fighters by the Nusra Front in exchange for individuals held by Lebanon. The first stage of the swap took place overnight.
Last week, Hezbollah captured most of the mountainous zone of Jroud Arsal from the militants.
The Nusra Front now spearheads the Tahrir Al Sham alliance in the Syrian civil war.