A group of Turkish non-governmental organizations gathered late Tuesday in front of the Russian embassy here to protest attacks on civilian structures in Syria's northwestern city of Aleppo.
"Last night, the world saw one of the deadliest nights of history," said Ismail Yildiz, chairman of the Union of Educationalist Public Employees.
"Last night around 100,000 civilians were trapped in Aleppo in an area of six square kilometers forced by Russia-supported regime forces," he said.
The NGOs, including the Youth Wing of Great Unity Party, TUGVA-Turkey Youth Foundation, Foundation of Erbakan and Dome Association, condemned the "massacre" in Aleppo "by Russia, Iran, and the Syrian regime".
Yildiz said the situation is so dire that fathers in the besieged city asked religious authorities for permission "to kill their own children so as not to leave them to the hands of the regime forces".
Violence has recently escalated in the city as Syrian regime forces advanced into opposition-held parts of eastern Aleppo on Monday following a five-month siege and persistent aerial bombardments.
The Russia-backed Bashar al-Assad regime had been trying to reestablish control over parts of Aleppo captured four years ago by armed opposition groups.
Since mid-November, more than 1,071 civilians have been killed in eastern Aleppo in attacks by Syrian regime and Russian warplanes, according to local sources.
Fierce bombardments have forced most of the city's hospitals to halt operations, while most academic activities have been indefinitely suspended.
According to a truce reached Tuesday between Syrian opposition forces and regime forces -- confirmed by Turkish Foreign Ministry spokesman Huseyin Muftuoglu -- civilians trapped in the conflict-hit zone will be moved via buses to the western side of Aleppo.
Turkish intelligence officials, who spoke on condition of anonymity due to restrictions on talking to media, said the cease-fire deal came after Turkey-brokered talks with Russia.
Meanwhile, Kremlin spokesperson Dmitriy Peskov told Russian RT channel late Tuesday that Russia and Turkey continued to cooperate on Syria and both countries agreed on the territorial and political integrity of Syria.
Peskov said President Recep Tayyip Erdogan and his Russian counterpart, Vladimir Putin, maintained close dialogue on the matter.
Syria has been locked in a devastating civil war since early 2011, when the Bashar al-Assad regime cracked down on pro-democracy protests -- which had erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.
Since then, hundreds of thousands of people are believed to have been killed and millions more displaced by the conflict.