At least 43 civilians, including five children, were killed on Monday in air strikes on Syria's northern Aleppo province, despite a "de-escalation zone" in place there, a monitor said.
The Britain-based Syrian Observatory for Human Rights said it was not immediately clear whether the strikes on the rebel-held town of Atareb had been carried out by Syrian warplanes, or those of Damascus's ally Russia.
The monitor said three strikes hit the town's market, adding that the overall toll was expected to rise because dozens of people had been wounded or were still missing after the attack.
The injured were transferred to the nearby field hospitals. Pro-opposition Syrian civil defense teams (White Helmets) rushed to the scene to rescue people stuck under the debris.
Four of the wounded persons were sent to Turkey for treatment, according to local sources from southeastern Turkish province of Hatay.
The sources told Anadolu Agency the injured people were referred to several hospitals in the province after initial treatment at the Cilvegozu border gate between Turkey and Syria.
Atareb is in the west of Aleppo province, in an area that is part of a "de-escalation zone" agreed under a deal earlier this year between Syria's allies Russia and Iran, and rebel backer Turkey.
Despite the government's recapture of Aleppo city late last year, rebel groups maintain a presence in the west of the province.
Syria has been in turmoil by a devastating civil war that began in early 2011 when the Assad regime cracked down on pro-democracy protests with unexpected ferocity.
Since then, hundreds of thousands of people have been killed in the conflict and more than 10 million displaced, according to the UN.
