LVIV, Ukraine (Reuters) - The situation in Ukraine's capital Kyiv is "difficult but under control", mayor Vitali Klitschko said on Thursday.

       Klitschko said there were no casualties overnight and that nighttime explosions were Ukrainian air defences striking down incoming Russian missiles. He said a heating system site damaged by Russian shelling on Wednesday would be fixed during the day.

       (Reporting by Natalia Zinets, Pavel Polityuk; Writing by Gabriela Baczynska; Editing by Alison Williams)