KYIV (Reuters) -Two people were killed and at least 14 wounded when a Russian drone smashed into a residential high-rise in Ukraine's Black Sea city of Odesa, authorities said on Saturday. Three children were among the wounded in the overnight attack, with one in critical condition, said regional Governor Oleh Kiper. Footage posted by the State Emergency Service showed firefighters battling a blaze and rushing residents down a dark stairwell in the 21-storey building. Russia has stepped up drone and missile strikes on Ukrainian cities in recent weeks as diplomatic efforts to end the nearly three-and-a-half-year-old war have stalled. (Reporting by Dan Peleschuk; Editing by William Mallard)