At least fifteen children have been killed when an air strike hit a school shelter in eastern Ghouta, on the outskirts of the Syrian capital Damascus, a conflict monitor says.
The Syrian Observatory for Human Rights said planes believed to be Russian hit the school shelter, which was being used by civilians.
"Usually regime planes do not fly at night, but Russian warplanes do," said activist Nour Adam.
Fifty-two people were wounded in the strike on the enclave, which has been a rebel stronghold since 2012. Syrian government forces backed by Russian air power began a major operation to retake Eastern Ghouta a month ago.
Activists in the area described the scene as "horrific" and said the bodies of small children were everywhere.
The death toll was likely to increase as some of the injured have serious wounds, Observatory head Rami Abdel-Rahman told dpa.
"Those people were hiding in the basement of the school thinking schools will not be hit, but for this tyrant (Syrian President Bashar al-Assad) and his allies the Russians there are no safe areas inside eastern Ghouta, all for them are terrorists, even the children," Abdel-Rahman said.
Since launching their assault, Syrian government forces have advanced deep inside the enclave and split it up, triggering a mass exodus from the area, which UN Secretary General Antonio Guterres has called "hell on earth".
Around 50,000 civilians have fled the embattled region to government-controlled areas since Thursday alone, according to Observatory estimates.
And at least 1454 people are thought to have been killed in eastern Ghouta, including 297 children and 183 women, the Britain-based watchdog says.
The humanitarian situation in eastern Ghouta is dire, according to the United Nations and the Red Cross. The two organisations have only been able to bring in small amounts of aid recently, reporting hunger and medicine shortages there.
