Russia said on Monday its forces have entered the north-eastern border town of Vovchansk, near Ukraine's second largest city Kharkiv, BBC reported.

Ukraine says there is still heavy fighting taking place there.

Russia has intensified its attacks on the region following Friday's surprise incursions across the border, seizing at least nine villages and settlements in one of the most significant ground attacks since its full-scale invasion of Ukraine in February 2022.

Ukraine's army has said that Russia has deployed "significant forces" - up to five battalions - in its latest offensive, acknowledging it had had "tactical success".

But in a statement, the army claimed that Russia had lost more than 100 troops in a day, adding that it was taking steps to repel advancing forces.