KYIV (Reuters) - Russian troops are slowly advancing towards the centre of the city of Sievierodonetsk in Ukraine's eastern Luhansk region, regional governor Serhiy Gaidai told Ukrainian state television on Tuesday.

       Gaidai said Ukrainian troops defending Sievierodonetsk were not at risk of being encircled as they could retreat to Lysychansk across the river.

       (Reporting by Pavel Polityuk; Writing by Olzhas Auyezov; Editing by Jacqueline Wong)