By Katharina Krebs and Kara Fox, CNN
(CNN) - Russian officials have criticized their military leadership following the retreat of Russian forces from the strategic eastern city of Lyman, in the Donetsk region, underlining concerns that Moscow could be eyeing nuclear weapons on the battlefield.
A Russian lawmaker and former army commander told Soloviev Live, a digital pro-Kremlin channel on Saturday that he could not explain this "surrender" from a military point of view.
"It is not clear to me why they didn't correctly assess the situation at that time, didn't strengthen the group of troops," Russian State Duma deputy and former commander of the 58th Army, Lieutenant General Andrei Gurulev said.
"This is probably a significant milestone not only military, but also political, especially now," he also said, adding that "the problem is the general lies, the report of a good situation. This system goes from top to bottom."
Using the Russian name for the town of Lyman, the Russian defense ministry said Saturday that that "troops were withdrawn from the settlement of Krasny Liman to more advantageous lines."
Russian state media Russia-24 reported that the reason for Russia's withdrawal was because "the enemy used both Western-made artillery and intelligence from North Atlantic alliance countries."
The retreat marks Ukraine's most significant gain since its successful counteroffensive in the northeastern Kharkiv region last month.
Ukrainian President Volodymyr Zelensky said Sunday that Lyman had been "completely liberated."
NATO Secretary General Jens Stoltenberg told NBC's "Meet the Press" on Sunday that the liberation shows "Ukrainians are making progress" and are "able to push back the Russian forces."
While it is unusual for pro-Kremlin outlets to carry any criticism of Russian authorities, there has been an increase in on-air criticism from hardliners -- who think Moscow should double down its military operation in Ukraine -- amid a series of military setbacks.
The leader of Chechnya, Ramzan Kadyrov, also criticized Russia's withdrawal on Saturday, saying in an angry statement slamming Russian generals in the wake of the withdrawal that the troops "were not provided with the necessary communication, interaction and the supply of ammunition."
Writing on Telegram, Kadyrov blamed the commander of the Central Military District Alexander Lapin, accusing him of moving his headquarters to Starobelsk, "a hundred kilometers away from his subordinates," and that he "was holed up in Luhansk."
"It's not a shame that Lapin is mediocre, but the fact that he is covered at the top by the leaders in the General Staff," he said in a Saturday post, adding that "there is no place for nepotism in the army, especially in difficult times."
He also said that it was time for the Kremlin to make use of every weapon at his disposal, adding to fears that pressure could to be growing on Russian President Vladimir Putin to use nuclear weapons on the battlefield.
"In my personal opinion we need to take more drastic measures, including declaring martial law in the border territories and using low-yield nuclear weapons," Kadyrov said. "There is no need to make every decision with the Western American community in mind."
Earlier this week, former Russian president Dmitry Medvedev, discussed the use of nuclear weapons on his Telegram channel, saying it was permitted if the existence of the Russian state was threatened by an attack even by conventional forces.
"If the threat to Russia exceeds our established threat limit, we will have to respond ... this is certainly not a bluff," he wrote.
Concerns about the use of nuclear weapons rose sharply after Putin's proclamation on Friday that Russia would seize nearly a fifth of Ukraine, declaring that the millions of people living there would be Russian citizens "forever."
The announcement was dismissed as illegal by the West, but the fear is the Kremlin might argue that attacks on those territories now constitute attacks on Russia.
In his speech in the Kremlin, Putin made only passing reference to nuclear weapons, noting the US was the only country to have used them on the battlefield.
"They created a precedent," he said.
Meanwhile, US Secretary of Defense Lloyd Austin has condemned "nuclear saber-rattling," telling CNN while he hasn't seen anything to suggest Putin has decided to use nuclear weapons in the ongoing war on Ukraine, the choice is up to the Russian President.
"To be clear, the guy who makes that decision, I mean, it's one man," Austin said.
"There are no checks on Mr. Putin. Just as he made the irresponsible decision to invade Ukraine, you know, he could make another decision. But I don't see anything right now that would lead me to believe that he has made such a decision," Austin added.
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