Russian forces have, in recent days, made small but significant gains right along the border in the Kharkiv region.
Their advances are only a few miles deep but have swallowed up around 100km (62 miles) of Ukrainian territory. In the more heavily defended east of Ukraine, it’s taken Russia months to achieve the same.
Russia claims its forces have now entered the border town of Vovchansk, which Ukraine disputes.
Ukraine’s military chief has said its forces are doing all they can to hold the line in Kharkiv but they are facing a "difficult situation".
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