The strikes destroyed 20 vehicles and three weapons depots in Islamic State-held Palmyra, state television said, quoting a military source. In Aleppo, they hit the towns of Al-Bab and Deir Hafer, about 20 km (10 miles) east of a military airport currently besieged by Islamic State fighters, Reuters said.
The Syrian Observatory for Human Rights, a Britain-based group tracking Syria's civil war, said the Palmyra strikes killed 15 Islamic State fighters.
"It was the heaviest Russian attack on Palmyra," Observatory director Rami Abdulrahman said. Across Syria, Russian jets carried out at least 34 air strikes in the last 24 hours, the Observatory said.
Another four Islamic State fighters were killed near Raqqa, the eastern city which has been the group's stronghold in Syria for the last two years.