Russia is calling in troops based in its far east to join the battle in Ukraine, the Ukrainian military high command said on Saturday, as Moscow seeks to reinforce its war-fighting force amid heavy losses and signs that its drive to seize eastern Ukraine has stalled.
Adding to the sense that both sides appeared to be girding for a war of attrition, Ukrainians on Saturday lined up at gas stations across the country as the government struggled to deal with a fuel shortage caused by Russian attacks on oil infrastructure.
“Queues and rising prices at gas stations are seen in many regions of our country,” President Volodymyr Zelensky of Ukraine said Friday in his nightly address. “The occupiers are deliberately destroying the infrastructure for the production, supply and storage of fuel.”
He said a Russian blockade of Ukrainian seaports meant that replacement stocks could not come in by tanker. The war has also paralyzed grain harvests in Ukraine, known as Europe’s breadbasket, disrupting global food supplies and worsening a food crisis in East Africa.
As Western allies have poured more heavy weapons into Ukraine, Slovakia and Poland, both NATO countries, reached an agreement that could presage the transfer of MIG-29 warplanes to Ukraine. Slovakia said that Polish F-16 jets would patrol its skies, freeing up a Slovak fleet of the Soviet-made MIGs.
After a meeting between the two countries’ defense ministers on Friday, Poland said its air force would begin patrols over Slovakia as part of their joint efforts to help Ukraine.
Slovakia did not say explicitly that it would send its MIGs to Ukraine, but it has raised the possibility of doing so — provided that it can find an alternative way to protect its airspace, which the agreement with Poland would seem to achieve.
Poland last month declined to provide its own fleet of MIG-29s to Ukraine directly, instead offering to fly the planes to a United States military base in Germany, where they could then be flown to Ukraine. Washington, worried about provoking Russia, declined the offer.
Russia’s foreign minister, Sergey V. Lavrov, contended that the United States and the European Union, by supplying more powerful weapons to Ukraine, were waging a proxy battle against Russia, regardless of the cost in civilian lives.
The flow of weapons from the West, Mr. Lavrov said, had nothing to do with supporting Ukraine’s sovereignty, but rather would enable the United States and the European Union to battle Russia “to the last Ukrainian.”
The fuel shortages in Ukraine followed Russian attacks this week on Ukraine’s main producer of fuel products and other large refineries. Russia said it had also hit storage facilities for petroleum products used by the Ukrainian military.
A senior Pentagon official said these types of attacks were intended to undercut the Ukrainian military’s ability to “replenish their own stores and to reinforce themselves.”
In response, officials in Kyiv, Ukraine’s capital, urged residents to use public transportation rather than private vehicles to save fuel. “We need to keep in mind the needs of the military and our defenders,” the city’s administration said.
The Kremlin’s deployment of troops from eastern Russia to the battle front in Ukraine suggested that Moscow could be trying to regain momentum in what the Pentagon has described as a “plodding” offensive in eastern Ukraine.
The Ukrainian military said that the additional Russian forces were being sent first to a Russian city near the Ukrainian border and then to the northeastern Ukrainian city of Izium, where the Russians have met fierce resistance. It did not say how many troops were being deployed.
Western analysts have said Russia’s offensive in the east has slowed as it struggles to overcome many of the same logistical problems involving shipments of food, fuel, weapons and ammunition that hampered the initial phase of its invasion more than two months ago.
On Saturday, the British Defense Ministry said Russia was trying to fix issues that had constrained its invasion by geographically concentrating combat power, shortening supply lines and simplifying command and control.
But Russia “still faces considerable challenges,” the ministry said in its latest intelligence update on the war. “It has been forced to merge and redeploy depleted and disparate units from the failed advances in northeast Ukraine. Many of these units are likely suffering from weakened morale.”
The fighting in eastern Ukraine has exacted an increasingly heavy toll on both militaries. The Russian Defense Ministry said on Saturday that its forces had fired on 389 targets across Ukraine, including facilities housing soldiers, killing 120 Ukrainians.
Ukraine said its Special Forces struck a command center near Izium, destroying dozens of tanks and armored vehicles.
In a measure of the rising toll on civilians, the Ukrainian authorities said the police had received more than 7,000 reports of missing people since the start of the invasion on Feb. 24, with half of the cases still unsolved.
Ukrainian officials called the number “unprecedented in modern history,” and they appealed to allies to send forensic experts and specialists in managing missing-persons registries.
In a long-awaited but frequently frustrated development in Mariupol, the ruined southern Ukrainian port occupied by Russian forces, about 20 women and children were evacuated from the Azovstal steel plant where the city’s last Ukrainian fighters have been holed up along with hundreds of increasingly desperate civilians.
The news, from Capt. Svyatoslav Palamar, the deputy commander of the Azov regiment, came amid United Nations-backed efforts to broker a cease-fire to allow the trapped civilians and Ukrainian fighters to escape the plant.
Captain Palamar said in a video posted to Telegram that an evacuation column had arrived in the evening to bring the civilians to a safe place, adding that he hoped wounded soldiers would be given safe passage as well.
He did not provide further details, though Russia’s TASS news agency said one of its correspondents on the scene reported that 25 people — including six children — had walked out of the plant. It was not immediately clear whether they were free to seek safety in Ukraine or were being held by Russian forces.
Nearly a million Ukrainians have been moved from Ukraine to Russia, Mr. Lavrov said in an interview published by Chinese state news media on Saturday. He described the moves as voluntary “evacuations,” a claim that contradicted witnesses, Ukrainian officials and Western observers who have said that many Ukrainians have been forcibly deported.
Mr. Lavrov’s claim echoed the false assertions in Russian propaganda that its forces are liberating ethnic Russians and others in Ukraine from what President Vladimir V. Putin of Russia calls the “openly neo-Nazi” Ukrainian government.
Ukraine has argued that Russia is carrying out the forcible migration of its citizens, which is a war crime, to be used as leverage in any peace talks.
Ukraine has also accused Russian forces of stealing cultural artifacts from occupied cities.
In Mariupol, city officials said Russian forces had taken more than 2,000 items — including icons, medals and works by Russian painters — from the city’s museums to Donetsk, the capital of an eastern region controlled by Moscow-backed separatists.
In the southern Ukrainian city of Melitopol, local officials said that a mysterious man in a white lab coat had used long tweezers and gloves to extract scores of gold artifacts more than 2,300 years old from cardboard boxes in a local museum, as a squad of Russian soldiers stood behind him with guns, watching eagerly. The items were from the Scythian empire and dated back to the fourth century B.C.
“The orcs have taken hold of our Scythian gold,” declared Melitopol’s mayor, Ivan Fyodorov, using a derogatory term many Ukrainians reserve for Russian soldiers. “This is one of the largest and most expensive collections in Ukraine, and today we don’t know where they took it.”
A series of explosions inside Russia in recent weeks have also increased concerns about the war spilling beyond Ukraine’s borders and set off the first air-raid siren on Russian soil since World War II.
The incidents include a Russian fuel depot that burst into flames moments after surveillance video captured bright streaks of rockets fired from low-flying helicopters, and a fire that broke out at a military research institute near Moscow.
Russia has accused Ukraine of carrying out the helicopter strike, while military analysts have suggested that Ukrainian sabotage was probably responsible for other fires. Ukraine has responded with deliberate ambiguity.
“We don’t confirm, and we don’t deny,” Oleksei Arestovych, an adviser to Mr. Zelensky’s chief of staff, said in an interview.
Mr. Arestovych described the policy as a strategic stance, and he compared it with Israel’s longstanding policy of ambiguity on nuclear arms, another issue of extraordinary geopolitical sensitivity.
“After what has been happening,” he said, “officially we don’t say yes and we don’t say no, just like Israel.”
Reporting was contributed by Steven Erlanger, Andrew Higgins, Maria Varenikova, John Ismay, Dave Philipps, Valeriya Safronova, Lauren McCarthy, Victoria Kim, Christiaan Triebert, Aleksandra Koroleva, Andrew E. Kramer, Jeffrey Gettleman, Michael Schwirtz and Christine Hauser.