Syrian government warplanes carried out several air strikes and low-level clashes have persisted in some but a Russian and Turkish-backed ceasefire has largely held on its third day, a monitoring group and rebels say.
Jets bombed the villages of Kafr Kar, Mintar and around the town of Banan in the southern Aleppo countryside, the British-based Syrian Observatory for Human Rights said on Sunday.
It said government forces also advanced overnight against rebels in the Eastern Ghouta area near Damascus, seizing 10 farms.
But opposition groups did not follow through on threats made on Saturday to abandon the truce altogether, raising hopes for an end to almost six years of fighting.
A military news outlet run by Lebanese group Hezbollah, an ally of Syrian President Bashar al-Assad, said the Syrian army had destroyed an armoured vehicle belonging to the former Nusra Front in southern Aleppo province.
The army has said the group, previously al Qaeda's Syria branch, is not included in the ceasefire deal but rebels say it is.
The latest truce agreement is the first not to involve the United States or the United Nations - a reflection of Moscow's growing diplomatic influence after a long campaign of Russian air strikes helped Assad recapture the northern city of Aleppo last month.
That victory has greatly strengthened the president's position as the warring sides prepare for peace talks in the Kazakh capital Astana this month.
Mohammed Rasheed, a spokesman for the Jaish al-Nasr rebel group operating mostly in the western province of Hama, said the area was mostly calm. There were low-level clashes in Wadi Barada near Damascus but government forces and their allies had stopped carrying out air strikes and shelling, he said.
The Hezbollah-run news outlet said during the night that government forces were fighting against the former Nusra Front in that area and had killed several militants.
The rebels warned on Saturday they would abandon the truce if government truce violations persisted, giving an 8pm local time deadline for attacks in Wadi Barada to stop. The shelling and air raids ceased by that time, rebels said.