Russia's Defense Ministry said Saturday it had resumed "offensive actions" in Ukraine after announcing a ceasefire earlier in the day to allow residents of two besieged cities to evacuate."Due to the unwillingness of the Ukrainian side to influence nationalists or extend the regime of silence, offensive actions have been resumed at 18:00 Moscow time (15:00 GMT)," Defense Ministry spokesman Igor Konashenkov said in a video briefing.Earlier on Saturday, Russia announced a ceasefire and said it opened humanitarian corridors for the exit of civilians from the strategic port town of Mariupol and neighboring Volnovakha.Konashenkov said that "not a single civilian" was able to exit via the humanitarian corridors."The population of these cities is held by nationalist formations as a human shield," Konashenkov added.He said "nationalist battalions" used the ceasefire to "regroup and reinforce their positions."Officials in Mariupol, surrounded by Russian forces, said Saturday they were delaying an evacuation of the civilian population, accusing Moscow's troops of breaking a ceasefire.