New air strikes on the town of Binnish in Idlib province in Syria's northwest have killed at least 14 people.
Fighting also appeared to continue on Tuesday inside and around the city of Aleppo, 50km from Idlib city, according to the British-based monitoring group, the Syrian Observatory for Human Rights.
Government forces and rebels in Aleppo had initially agreed on Monday to extend their truce for a second time, according to the army, as the United States and Russia vowed to "redouble" efforts to end the five-year conflict.
The cessation of hostilities was initially to last for two days but was later extended until Tuesday at 00:01 am (21:01 GMT Monday).
Announcing a further prolongation, the army command said: "The "regime of silence" in Aleppo and its province has been extended by 48 hours from Tuesday 01:00 am [local time] to midnight on Wednesday."
The US and Russia also agreed to try extend a February 27 ceasefire across the whole of the country.
But Tuesday's deadly airborne raids, by either Syrian or Russian warplanes wounded dozens of other Syrians, the Observatory said.
A local rebel commander was among those killed. There were no immediate details about other casualties.
Idlib province, which borders Turkey, is almost completely controlled by rebel groups, including the al-Qaeda-affiliated al-Nusra Front along with Ahrar al-Sham.
Washington and Moscow on Monday hailed some "progress" in reducing the fighting but admitted to ongoing "difficulties" in achieving a de-escalation in some areas as well as in ensuring humanitarian access to besieged areas.
On Sunday, Syrian rebels fired rockets into a regime-held district of Aleppo, killing five civilians including two children, the Observatory reported.
Source: Al Jazeera and agencies