According to the Britain-based Syrian Observatory for Human Rights, clashes in north-western Syria killed four regime fighters and one rebel on Tuesday despite a 12-day-old truce.
The clashes occurred in the south of Syria’s last rebel bastion of Idlib, a region covered by a ceasefire that entered into force on March 6.
Before dawn on the truce’s first day, an exchange of fire killed six regime fighters and nine jihadists, but belligerents have largely respected it since.
Despite Tuesday’s clashes, regime and Russian aircraft remained absent from the skies over the region, Observatory head Rami Abdel Rahman said.
The ceasefire agreed by regime ally Russia and rebel backer Turkey had raised hopes it would stem a months-long government assault on the rebel bastion, which is home to some three million people.
Residents have said they are skeptical about the ceasefire holding however, especially as Damascus has repeatedly said it would eventually bring all of Syria back under its control.
Syria’s civil war has killed more than 380,000 people and displaced millions since starting nine years ago with the brutal repression of anti-government protests.