Syrian regime and Russian air strikes on Sunday killed 57 civilians, among them 19 children, in rebel-held Eastern Ghouta region and in a village held by the Islamic State group in Syria's eastern Deir Ezzor province, a monitor said.
The Britain-based Syrian Observatory for Human Rights said strikes that hit the village of Al-Shafah, on the eastern bank of the Euphrates River, in the early hours of Sunday morning, killed 19 adults and 15 children.
The Observatory relies on a network of sources inside Syria, and says it determines whose planes carry out raids according to type, location, flight patterns and munitions used.
Russia is a close ally of Syria's President Bashar al-Assad, and in September 2015 began a military intervention in support of his government that has gradually helped Damascus regain territory.

The regime air strikes and artillery fire in Eastern Ghouta region killed 23 civilians including 4 children.  The deaths come despite the area falling within a so-called "de-escalation zone" put in place under a deal between government allies Russia and Iran and rebel backer Turkey.
Eastern Ghouta is already in the grip of a humanitarian crisis caused by a crushing regime siege of the area since 2013 that has caused severe food and medical shortages.
The oil-rich eastern province that borders Iraq was once almost completely under IS control, but the jihadists now hold just nine percent of Deir Ezzor, according to the Observatory.
They have faced two separate offensives there, one led by the regime with Russian backing and the other by the US-backed Syrian Democratic Forces, an alliance of Kurdish and Arab fighters.
More than 340,000 people have been killed in Syria since the conflict began in March 2011 with anti-government protests.
Related Story