Ukraine said on Tuesday the last 24 hours were the deadliest of the war so far for Russian troops as Moscow pressed on with an intensifying winter assault in the east, bringing tens of thousands of freshly mobilized troops to the battlefield.
The Ukrainian claim could not be independently verified and Russia has also claimed to have killed large numbers of Ukrainian troops in recent weeks. Tallies of enemy casualties from either side have typically been seen as unreliable, and Kyiv offered few details of the latest battles.
But the assertion that the fighting was the deadliest so far fits descriptions from both sides of an escalating campaign of close-contact trench warfare, which has left snow-covered battlefields of eastern Ukraine littered with corpses.
Close to the town of Maryinka, some 30 km (18.6 miles) from the eastern city of Donetsk, a marine unit of Ukraine's armed forces fired rockets on Russian positions from a Soviet-era launch system.
"They storm in small infantry groups, trying to creep in further and further. Even without previous artillery strikes (on Ukrainian positions), their infantry attempts to move in," said a soldier who gave his name only as Ievhen.
"The enemy adapted quite well, they learn as fast as we do. They adopted different kinds of tactics," he added.
Kyiv and the West say Russia has been pouring troops and mercenaries into eastern Ukraine in recent weeks in hopes of being able to claim new gains around the time of the first anniversary of its full-scale invasion later this month.
A lieutenant in the Ukrainian unit who gave his name as Volodymyr said: "The targets are given to us either by drone operators or by our spotters - they observe where our rockets explode. Then, we correct our fire direction and launch again."
The Ukrainian military increased its running tally of Russian military dead by 1,030 overnight to 133,190, and described the increase as the highest of the war so far. For its part, Russia said it had inflicted 6,500 Ukrainian casualties in the month of January.
The war is soon entering its second year at a pivotal juncture, with Moscow attempting to regain the initiative while Kyiv holds out for Western tanks to mount a counter-offensive later in 2023.
After Russia failed to capture the Ukrainian capital Kyiv last year and lost ground in the second half of 2022, Moscow is now making full use of hundreds of thousands of troops it called up in its first mobilization since World War Two.
The last few weeks have seen Russia boast its first gains for half a year. But the progress has still been incremental, with Moscow yet to capture a single major population center in its winter campaign despite thousands of dead.
Fighting has focused for months around Ukrainian-held Bakhmut in eastern Donetsk province, a city with a pre-war population of around 75,000. Russia has made clear progress towards encircling it from both the north and south, but Kyiv says its garrison is holding fast.
Moscow has also launched an assault further south against Vuhledar, a Ukrainian-controlled bastion also in Donetsk province on high ground at the strategic intersection between the eastern and southern front lines.
No word from Zelensky on defense minister
Since the New Year, Western countries have pledged hundreds of tanks and armored vehicles to Ukraine to give it the firepower and mobility to push through Russian lines and recapture occupied territory later this year.
A new US package of weapons is expected to include longer-range rockets, which would give Ukraine the ability to hit Russian supply lines in all of the territory it occupies in Ukraine's mainland and parts of the Crimea peninsula.
But it will take months before they arrive, and meanwhile, Ukraine faces a Russian force with its manpower replenished by Moscow's call-up of reservists. The Kremlin says Western supplies of arms only widen and extend the conflict.
"The US and its allies are trying to prolong the conflict as much as possible," Russian Defence Minister Sergei Shoigu said on Tuesday in a conference call with military officials.
"To do this, they have started supplying heavy offensive weapons, openly urging Ukraine to seize our territories. In fact, such steps are dragging NATO countries into the conflict and could lead to an unpredictable level of escalation."
His use of the phrase "our territories" appeared to refer to four Ukrainian provinces Russia claimed to have annexed last year, as well as Crimea, which it seized from Ukraine in 2014.
In a daily intelligence update, Britain's Defense Ministry said Russia's military had been trying since early January to restart major offensive operations to capture Ukraine-held parts of Donetsk region but had gained little ground so far.
The Russians "lack munitions and maneuver units required for a successful offensive," it said.
Ukrainian officials say Moscow could be accumulating weapons and reserves for an even bigger push in the coming weeks. The Ukrainian governor of Luhansk province predicted a big Russian offensive there that could begin around Feb. 15.
The past few weeks meanwhile have seen a purge of Ukrainian officials in an anti-corruption campaign, the first big shake-up of Ukraine's leadership since the war began.
In his Monday evening address, Ukrainian President Volodymyr Zelenskiy said personnel changes on the border and frontline would bolster Ukraine's military efforts.
But he gave no indication about the fate of his defense minister, Oleksii Reznikov. The head of a parliamentary faction of Zelensky's party had said on Sunday that Reznikov would be replaced, but said on Monday no changes would be made this week.