Putin's Lyman Defeat a Major Setback as Undermanned Forces Lose City: U.K.

Russia's defeat in the strategic Ukrainian city of Lyman is a "significant political setback," according to the U.K.'s Ministry of Defence.

Russia's loss of Lyman, Which is located in the Donetsk region and was being used as a transport and logistics hub, presented a fresh blow to Russian President Vladimir Putin as he escalated the war by annexing four regions of Ukraine.

Russia's Defense Ministry confirmed that it had "retreated to more advantageous lines," Russian-state news agency RIA reported.

In a daily intelligence briefing on Sunday, Britain's defense ministry said Lyman was "likely being defended by undermanned elements of Russia's Western and Central Military Districts, as well as contingents of voluntarily mobilized reservists."

"The force probably experienced heavy casualties as it withdrew along the only road out of the town still in Russian hands," it added.

The city is important, the report said, because it has "a key road crossing over the Siversky Donets River, behind which Russia has been attempting to consolidate its defenses."

It noted that Russia's withdrawal from Lyman "also represents a significant political setback given that it is located within Donetsk Oblast, a region Russia supposedly aimed to 'liberate' and has attempted to illegally annex."

Moscow's withdrawal from Lyman has prompted further criticism of Russia's military leadership from some Russian officials, U.K. officials said.

"Further losses of territory in illegally occupied territories will almost certainly lead to an intensification of this public criticism and increase the pressure on senior commanders," the briefing added.

Ukrainian forces have retaken large swathes of territory in a counteroffensive that started in September.

Facing mounting losses, Putin ordered a partial military mobilization and annexed four regions of Ukraine, including Donetsk.

On Saturday, footage of Ukrainian soldiers hoisting their flag on the outskirts of Lyman, which has been occupied by Russia since May, were widely shared on social media.

"The Ukrainian flag is already in Lyman," Ukrainian President Volodymyr Zelenskyy said in his nightly address.

"Over the past week, there have been more Ukrainian flags in the Donbas. In a week there will be even more."

That came a day after Putin proclaimed the annexation of four Ukrainian regions after holding what Russia called referendums in occupied areas of Ukraine, which have been met with global condemnation.

"Russia is violating international law, trampling on the United Nations Charter, and showing its contempt for peaceful nations everywhere," President Joe Biden said in a statement on Friday.

"Make no mistake: these actions have no legitimacy. The United States will always honor Ukraine's internationally recognized borders."

Newsweek has contacted Russia's Defense Ministry and Ukraine's Defense Ministry for comment.