Russian forces have become “bogged down” in attempts to seize the border-town Vovchansk, but have sharpened their offensive elsewhere along the eastern front, Ukraine’s top general said on Friday.

Kyiv has been battling a fresh Russian land assault on its northeastern Kharkiv region since May 10, when thousands of Moscow’s troops stormed the border, making their biggest territorial advances in 18 months.

Despite initial success , “the enemy has got completely bogged down in street battles for Vovchansk and suffered very high losses in assault units’, said Ukrainian commander-in-chief Oleksandr Syrsky on social media.

In an attempt to seize the town, Russia “is currently moving reserves from different sectors to support active assault operations, but to no avail”, Mr Syrsky added.

Although he warned that the situation on the eastern front was unstable, where Russia claims its forces have made a series of gains in the past two weeks.

Fighting near the eastern towns of Chasiv Yar, Pokrovsk and Kurakhove has been particularly “intense”, he added.

The fresh offensive on the region has seen more than 11,000 people evacuate.