Russian forces have made two cross-border assaults inside northern Ukraine, according to information from Ukrainian sources and officials, in what President Volodymyr Zelensky is calling a “new wave of counteroffensive actions” by Russia.

In the first development, Russian soldiers penetrated at least one kilometer towards the town of Vovchansk, a Ukrainian military source told CNN. The aim, the source said, “was to get 10 km deep and create a buffer zone at the border to secure Russian territory from feeling the war.”

In an official statement, Ukraine’s Defense Ministry said Russian soldiers supported by armored vehicles had moved across the border at about 5:00am Friday, following a day of stepped-up attacks on the border area with guided aerial bombs and artillery.

The statement added that Ukrainian reserve units had been deployed to strengthen defenses in the area.