Beirut: Air strikes killed at least 39 civilians on Saturday in Raqa, the Islamic State group`s main stronghold in Syria, a monitoring group said.
At least five children and seven women were among the dead, according to the Britain-based Syrian Observatory for Human Rights.
The raids came a day after 16 civilians were killed in strikes on the same city.
"We cannot know whether the latest strikes on Raqa are by Syrian or Russian warplanes," said Observatory director Rami Abdel Rahman.
"What is clear is that their goal is to try to paralyse IS and to stop it from deploying reinforcements from Raqa to the Palmyra area," he told AFP.
IS seized Palmyra, a UNESCO World Heritage Site known as the "Pearl of the Desert", last May.
In recent weeks, Syrian troops backed by the Russian air force have been pressing an advance to try to reclaim the ancient city.
On Saturday alone, Palmyra was hit by at least 70 strikes, the Observatory said.
Russia, a key backer of the Syrian regime, on Monday ordered the withdrawal of most of its armed forces from Syria, but continues to strike jihadist targets, particularly around Palmyra.