A Ukrainian unit said on Wednesday it had routed a Russian brigade near the stronghold of Bakhmut in an incident underlining the task facing the Kremlin as it carries out what it calls a “very difficult” military operation.

The unit’s claim appeared to buttress comments by Yevgeny Prigozhin, the head of the Wagner private army, who on Tuesday said the Russian brigade had abandoned its positions in Bakhmut, Moscow’s primary target in its winter offensive and scene of the bloodiest ground combat in Europe since World War Two.

Colonel General Oleksandr Syrskyi, who heads Ukraine’s ground forces, said Russian units in some parts of Bakhmut had retreated by up to two km (1.2 miles) as the result of counter attacks. He gave no details.

Reuters was unable to independently confirm the situation on the ground. Wagner units have led a months-long Russian assault on the eastern city, suffering heavy losses, but Ukrainian forces say the offensive is stalling.

“The special military operation continues. This is a very difficult operation, and, of course, certain goals have been achieved in a year,” Tass new agency quoted Kremlin spokesman Dmitry Peskov as telling a Bosnian Serb television channel.

“We managed to beat up the Ukrainian military machine quite a bit,” said Peskov, citing Russian missile strikes in Ukraine. “This work will continue”.

Peskov said he had no doubt that Bakhmut “will be captured and will be kept under control”. He also said the Russian campaign in eastern Ukraine was proceeding slowly because Russia “is not waging war”.

“Waging war is a completely different matter - it means complete destruction of infrastucture, it means complete destruction of cities,” he said. “We are not doing this. We are trying to preserve infrastructure and preserve human lives.”

Peskov’s comments did not address claims that Russia’s 72nd Separate Motor-rifle Brigade had abandoned positions on the southwestern outskirts of Bakhmut.

In a statement, Ukraine’s Third Separate Assault Brigade said: “It’s official.

Prigozhin’s report about the flight of Russia’s 72nd Independent Motorized Rifle Brigade from near Bakhmut and the ‘500 corpses’ of Russians left behind is true.“