Four air strikes hit rebel-held parts of Syria's Aleppo today, a monitor said, in the first raids on the battered city since a truce took effect.
The Syrian Observatory for Human Rights said several people were wounded but could not immediately give details about casualties or identify who carried out the strikes.
A halt to fighting around Aleppo and the delivery of desperately needed humanitarian aid were key components of the fragile truce, which began last Monday.
While the front lines had remained calm, civilians in the besieged eastern quarters had yet to receive promised food assistance.
The estimated 250,000 people in the eastern half of the city have been living under government siege since early September.
Rebel groups - which have yet to formally sign on to the truce - have regularly pledged to break the encirclement.
The head of Fateh al-Sham Front, which changed its name from Al-Nusra Front after renouncing its ties to Al-Qaeda, said yesterday that opposition fighters would do all they could to end the encirclement.
Abu Mohamed al-Jolani said "neither we nor rebel groups will allow the siege of Aleppo to continue".
More than 300,000 people have been killed since Syria's conflict erupted in March 2011 with protests calling for the removal of President Bashar al-Assad.
Meanwhile, fighters from the so-called Islamic State militant group shot down a Syrian military plane in the eastern Syrian city of Deir al-Zor, the Islamic State-affiliated news agency Amaq has reported.
"A Syrian warplane belonging to the Syrian regime was brought down when targeted by fighters from the Islamic State in the city of Deir al-Zor," Amaq said in an online statement.
The Syrian Observatory for Human Rights said the pilot of the MIG Syrian warplane was killed.
Elsewhere, the Australian Department of Defence offered its condolences to the families of Syrian soldiers killed or wounded in a US-led bombing campaign yesterday, in which Australia participated.
Australian aircraft were among the warplanes that struck what were believed to be IS fighting positions around Deir al-Zor in Eastern Syria.
However, shortly after the bombing started Russian officials advised the multinational Combined Air Operations Centre that the targets may have been Syrian military personnel.
The Australian Ministry of Defence said this morning that it would fully cooperate with a coalition review of the incident.
"While Syria remains a dynamic and complex operating environment, Australia would never intentionally target a known Syrian military unit or actively support Daesh [another name for the so-called Islamic State militant group]," the ministry said in a statement.
"Defence offers its condolences to the families of any Syrian personnel killed or wounded in this incident," the ministry said this morning.
