Putin said "Ukrainian nationalists" prevented civilians and foreign citizens from leaving the port city of Mariupol and neighbouring Volnovakha on Saturday despite a ceasefire announcement.
"And the pause in hostilities was again used only to build up forces and means in their positions," Putin told French President Emmanuel Macron.
Putin also assured Macron of the "physical and nuclear safety" of the Zaporizhzhia nuclear plant that was captured by Russian forces.
He also said Russian troops were in control of Ukraine's Chernobyl nuclear power plant, which is encased in a giant sarcophagus following an explosion in 1986 -- the worst nuclear accident in history.
"All this is being done in order to exclude the possibility of provocations fraught with catastrophic consequences by Ukrainian neo-Nazis or terrorists," the Kremlin added. According to the Elysee, the two leaders spoke for one hour and 45 minutes.