Russian troops have launched a new assault in Ukraine's north-east, with Kyiv rushing in reinforcements to the Kharkiv region as heavy fighting continues.

At least 4,000 residents have been evacuated from the area, as Russia claims it has taken up to nine villages since its troops crossed the border on Friday. Ukraine's president Vlodymyr Zelenskyy says halting Russia's offensive is the country's number one priority.

Guest: Michael Clarke, visiting Professor in the Department of War Studies at King's College London and former head of the Royal United Services Institute