At least half a dozen people are reported to have been killed in airstrikes on Syria's eastern Ghouta.
They came just hours after a UN resolution calling for a 30-day ceasefire in the rebel-held enclave to allow access for humanitarian aid.
During phone talks on Sunday, the leaders of France, Germany urged Russia - Syria's ally - to pressure the Assad regime to immediately enforce \the UN ceasefire.
The Kremlin said President Putin reacted positively and agreed to speed up their "exchange of information" on Syria.
Pope Francis also weighed in, calling for an immediate halt to what he called "inhuman" violence.