Syrian government forces have pressed their offensive in the province of Hama and captured a new city in Deir Az Zor, aiming to clear the country of Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.
The violence on Friday came as a deal was announced in the Kazakh capital of Astana on de-escalation in the nearby, mostly rebel-held province of Idlib.
Syrian troops have been on the offensive against ISIL in central Syria for weeks under the cover of Russian airstrikes. 
In August, troops were able to besiege a wide area controlled by the group that has been shrinking ever since.
One of the main battles has been taking place near the central town of Okeirbat, which government forces captured in mid-August.
Earlier this month, ISIL fighters regained control of the town only to lose it again on Thursday after a crushing attack that involved intense air attack, according to the Britain-based Syrian Observatory for Human Rights.
Okeirbat was the largest town ISIL held in the central province of Hama. The area is important because it is close to villages loyal to President Bashar al-Assad. 
If it loses the central region, ISIL will be mostly left in the eastern province of Deir Az Zor as well as a third of the northern city of Raqqa, once the group's de facto capital.
The Observatory said on Friday that more than two weeks of fighting has left hundreds dead on both sides.
The government-controlled Syrian Central Military Media reported the clashes, saying ISIL positions are being targeted with artillery and rockets.