“Militants violated the ceasefire. Army positions were shelled by mortar rounds near the Castillo Road in Aleppo,” the source said.
“The Syrian army responded the attacks with artillery fire, while the army units are ready to repel ground attacks by militants if necessary,” the source added.
The new nationwide ceasefire regime in Syria came into force on September 12.
On Monday, Syrian President Bashar al-Assad vowed to retake all of Syria from “terrorists”, hours before a ceasefire was to take effect in the evening.
“The Syrian government is determined to recover every area from the terrorists,” Assad told Syrian state media after he attended Eid al-Adha holiday prayers in Darayya, a former militant stronghold recently recaptured by the government.
The ceasefire will not include terrorist groups like ISIL and Fatah al-Sham Front (formerly known as al-Nusra Front).
The landmark deal, proposed by the United States and Russia after marathon talks in Geneva on Friday, could also lead to the first joint military operations by Moscow and Washington against terrorists.