Ukraine's security services said Saturday they had struck a Russian ammunition depot in a border region, as Moscow's forces claimed yet another advance on the battlefield.

Ukraine also said it had thwarted a "massive" overnight Russian aerial attack that saw drones launched towards the capital Kyiv.

The attacks come after a week of intense Russian bombardments across Ukraine that killed at least 55 in the central city of Poltava, and seven in Lviv — hundreds of kilometers from the front lines and close to Ukraine's western border with EU and NATO members.