MOSCOW (Reuters) - Russia said on Saturday that its forces had taken five border villages in Ukraine's Kharkiv region, where Russia launched an offensive on Friday, exploiting its increasing advantage on the battlefields of eastern Ukraine.

In its briefing on Saturday, the Defence Ministry said that Russian forces had taken the villages of Pletenivka, Ohirtseve, Borysivka, Pylna and Strilechna, all of which are directly on the Russian border.

The briefing also said that Russian troops had taken the village of Keramik in the Donetsk region further south, where Moscow has made slow but steady advances since seizing the longtime Ukrainian stronghold of Avdiivka in February.

Ukrainian officials said on Friday that Russia had launched a new cross-border offensive against Kharkiv region, which is centred around Kharkiv city, Ukraine's second largest.

Russia kept up its attacks in the Kharkiv region on Saturday and was trying to advance further, Kharkiv Governor Oleh Syniehubov said.

Russian forces first attacked Kharkiv region in Feb. 2022, but were routed from most of the province by a lightning Ukrainian counter-offensive in September of that year.

Russia's neighbouring Belgorod region has since come under regular Ukrainian drone and artillery strikes.

Asked in March whether Russian forces might need to take Kharkiv region, Russian President Vladimir Putin said that the only way to secure Russian territory from Ukrainian strikes was to create a buffer zone that would place Moscow's territory out of range of Kyiv's forces.

Russia controls about 18% of Ukraine - in the east and south - and has been gaining ground since the failure of Kyiv's 2023 counter-offensive to make any serious inroads against well dug-in Russian troops.

(Writing by Felix Light; Editing by Alison Williams/Guy Faulconbridge)