Signs of an imminent Ukrainian counteroffensive mounted on Monday with stepped-up military strikes by both sides, Russian forces moving into defensive positions and even an unexplained explosion that knocked a supply train off its tracks across the border in Russia.
Ukraine’s defense minister, Oleksii Reznikov, said in an appearance on national television that the military was “reaching the finish line” in preparations to launch a counteroffensive and that commanders would decide “how, where and when.”
The day began with Russia launching broad aerial assaults across Ukraine, its second wide-ranging attack in four days.
In Pavlograd, a city in central Ukraine, dozens of buildings were damaged, including schools and homes, local officials said, and missile strikes set off a massive fire that lit up the night sky. In Kyiv and elsewhere, explosions echoed across the pre-dawn landscape as air defenses shot down what the Ukrainian military said was 15 of 18 Russian cruise missiles.
Russia’s Ministry of Defense claimed its barrages were “a long-range high-precision air- and sea-based missile strike against Ukrainian military-industrial complex facilities.” But at least 34 people, including five children, were wounded in Pavlograd, local officials said.
But even as Moscow ratcheted up its attacks, its forces are bracing for a counteroffensive, moving into defensive positions in the south, according to Ukrainian and Western officials.
Britain’s defense intelligence agency said on Monday that Russia had “constructed some of the most extensive systems of military defensive works seen anywhere in the world for many decades,” not only near the front line but also “deep inside areas Russia currently controls.”
And in Washington, White House officials released new estimates that since December alone the Russian military has sustained a staggering 20,000 deaths in Ukraine.
With the warring armies emerging from a winter of heavy death but little advancement, Ukrainian forces, like the Russians, are turning up the pressure. There were growing reports of strikes deep behind enemy lines in Russian-occupied territory, with the apparent goal of degrading Russian forces ahead of what is widely expected to be a much bigger battle.
At day’s end, Ukraine reported that its pilots had carried out four strikes on areas where enemy personnel were concentrated. They said rocket and artillery fire had struck five areas where weapons and military equipment were concentrated, as well as an ammunition depot and a logistics center.
The Ukrainians had less to say about an explosion that was reported to have derailed a freight train in Russia’s Bryansk region on Monday, the latest in a spate of apparent attacks to hit the area bordering Ukraine.
Photos and videos circulating on social media showed a large fire burning and a train tilted askew, with at least one carriage lying on its side. Rybar, an influential pro-war Russian military blog that posted one of the videos, said that train cars carrying oil products and lumber were lying on their side.
The Russian railway company said in a statement that “an intrusion by unauthorized individuals” had set the locomotive on fire and blocked traffic on the rail line. The governor of the Bryansk region blamed an “unidentified explosive device” in a post on the Telegram messaging app. He did not say who was responsible.
Ukraine generally maintains a policy of strategic ambiguity about strikes on Russian territory, but its officials have reserved the right to strike targets within Russia that they say are used to attack Ukrainian towns and cities.
Ukrainian officials appeared divided Monday on the question of how citizens living in towns now controlled by the Russians should handle increasing pressure from the Kremlin to recognize its authority,
Last week, Russia’s president, Vladimir V. Putin, signed an edict declaring that all Ukrainians living in occupied territory who refuse Russian passports could be relocated from their homes, the latest sign of the Kremlin’s commitment to Russify areas of Ukraine under Russian control.
Mr. Putin made it clear that he regards the occupied territories as part of Russia, sticking to the nationalist rhetoric he has used to justify the war. “These are our historical lands and these people are our natives,” he said,
Ukraine’s human rights commissioner, Dmytro Lubinets, urged Ukrainians living under Russian occupation to cooperate for their own safety. “Take a passport, survive, wait until we liberate this territory,” he said.
But on Monday, Deputy Prime Minister Iryna Vereschuk offered a different message.
“Do not take Russian passports,” she said, urging citizens “not to cooperate with the occupiers.”
Ms. Vereschuk did echo Mr. Lubinets on one point: “Wait for the Armed Forces of Ukraine,” she said.
Reporting was contributed by Malachy Browne, Zolan Kanno-Youngs, Cassandra Vinograd, Ivan Nechepurenko and Anatoly Kurmanaev.
