Ukrainian forces have “highly likely” recaptured an area of territory occupied by Russia since 2014, the UK’s Ministry of Defence has said.
In a new intelligence update, British officials said small advances have been made east from Krasnohorivka near Donetsk, which sits on the old Line of Control.
“Recent multiple concurrent Ukrainian assaults throughout the Donbas” may have also left separatist forces in the area overstretched, the UK’s analysis added.
This is believed to be one of the first instances of gains being made since the war began last February.
On Monday, Ukrainian President Volodymyr Zelenskyy declared that his troops had made frontline advances “in all directions”.
He visited soldiers in the east and south of the country – including Donetsk and Zaporizhzhia – handing out awards and posing for photographs on a journey that spanned “hundreds of kilometres”.
And in his nightly video address delivered from a train, Mr Zelenskyy described it as a “happy day” where he met “absolutely heroic people”.
Sky’s defence and security analyst Professor Michael Clarke says Ukraine is capitalising on Russian chaos caused by Wagner’s rebellion over the weekend.
“They [the Ukrainians] have used this opportunity to increase the pressure all the way across the front to see where the gaps are,” he said.
Professor Clarke said Wagner troops made up a significant portion of the Russian frontlines – and questioned whether they would return following rest after the battle for Bakhmut and the recent mutiny.
He pointed out that the Volga and Wagner groups make up to 25% of the force fighting on the Russian frontline, meaning Putin’s regime “may have lost a rather important part of their reinforcement process”.
EU foreign policy chief Josep Borrell suggested that the attempted armed rebellion shows the war is “cracking Russia’s political system”.
He said: “The monster that Putin created with Wagner, the monster is biting him now. The monster is acting against his creator.”
Amid newfound momentum since his counteroffensive began, Mr Zelenskyy has held meetings with top generals on the Ukrainian military’s next steps.
The president has also been engaged in negotiations with allies, including US President Joe Biden, about weapons supply packages.
“All our land will be free – absolutely all of it,” his video address concluded.