KYIV (Reuters) - Fighting was under way on Saturday near the southern Ukrainian cities of Mariupol, Kherson, Mykolaiv, and Odessa, an adviser to the Ukrainian president's office said.

       "Heavy fighting is taking place near Mariupol," Mykhailo Podolyak, the adviser, told a briefing. "But there is no chance that Mariupol will surrender or be captured."

       (Reporting by Pavel Polityuk; Writing by Olzhas Auyezov; Editing by Sam Holmes)