Artillery fire escalated sharply in eastern Ukraine on Saturday and thousands of residents fled the region in chaotic evacuations — two developments rife with opportunities for what the United States has warned could be a pretext for a Russian invasion.
Russian-backed separatists, who have been fighting the Ukrainian government for years, have asserted, without evidence, that Ukraine was planning a large-scale attack on territory they control.
Western leaders have derided the notion that Ukraine would launch an attack while surrounded by Russian forces, and Ukrainian officials dismissed the claim as “a cynical Russian lie.”
But separatist leaders on Saturday urged women and children to evacuate, and able-bodied men to prepare to fight. And the ginned-up panic was already having real effects, with refugees frantically boarding buses to Russia and refugee tent camps popping up across the Russian border.
At the same time, the firing of mortars, artillery and rocket-propelled grenades by separatist rebels along the front line roughly doubled the level of the previous two days, the Ukrainian Ministry of Internal Affairs said. Two Ukrainian soldiers were killed and five wounded, the military said.
Ukrainian officials said the shelling came exclusively from the separatists, who are seen as a proxy for Russia.
New York Times reporters at the scene witnessed shelling from separatists and saw no return fire from the Ukrainian forces, although residents in the separatist regions said there was shelling from both sides.
“I have a small baby,” said Nadya Lapygina, who said her town in the breakaway region of Luhansk was hit by artillery and mortar fire. “You have no idea how scary it is to hide him from the shelling.”
In a pointed reminder of where this conflict could lead, Russia engaged in a dramatic display of military theater on Saturday, test-firing ballistic and cruise missiles. President Vladimir V. Putin of Russia presided over tests of nuclear-capable missiles as part of what Russia insists are nothing more than exercises and not the precursor to an invasion.
Tensions between the United States and Russia have not been this high since the Cold War, and Russia’s nuclear drills appeared carefully timed to deter the West from direct military involvement in Ukraine.
Western leaders gathering in Munich issued repeated calls for a diplomatic resolution to the crisis, despite President Biden’s claim on Friday that Mr. Putin had already decided to invade Ukraine.
The leaders displayed a remarkably united front in what Vice President Kamala Harris called “a defining moment” for European security and the defense of democratic values.
But in Ukraine, the fighting edged perilously closer to a tipping point. And there were alarming signs of what American officials described as possible precursors to a pretext for a Russian invasion.
Intense artillery barrages targeted a pocket of government-controlled territory around the town of Svitlodarsk, a spot that has worried security analysts for weeks for its proximity to dangerous industrial infrastructure, including storage tanks for poisonous gas.
A stray shell from returning government fire risks hitting a chemical plant about six miles away in separatist-controlled territory. The plant, one of Europe’s largest fertilizer factories, has pressurized tanks and more than 12 miles of pipelines holding poisonous ammonia gas.
An explosion there could produce a toxic cloud that could serve as an excuse for a Russian invasion or, American officials have warned, Russia could stage its own explosion there to justify intervention.
Another potential flash point in the area, a water network that supplies drinking water to several million people on both sides of the conflict, may have been damaged by shelling on Saturday. Russia’s Interfax news agency cited a spokesman for the self-proclaimed Donetsk People’s Republic saying that shelling had struck a pumping station and the water supply was at risk.
A loss of water for residents in the Russian-backed areas would reinforce Russian assertions of dire conditions for civilians and would be a setback for Ukraine, which has tried to persuade residents that the government is not their enemy. A cutoff of that water supply amid fighting in 2014 hastened a flow of refugees from the city.
In what Western officials dismissed as a baseless provocation, Denis Pushilin, the leader of one pro-Russia separatist region, the so-called Donetsk People’s Republic, called on all able-bodied men to be prepared to fight the coming Ukrainian assault.
“I appeal to all men of the republic who are able to hold weapons in their hands, to stand up for their families, their children, wives and mothers,” he wrote on social media.
The Kyiv government denied any plans for an attack, but the warnings still had residents flocking to bus depots in eastern Ukraine.
Inna Shalpa, a resident of the separatist-held town of Ilovaisk, in the Donetsk region, had no idea where the Russian bus she and her three children boarded was headed, but she was ready to accept the uncertainty to flee an expected war.
“We were mostly worried about the children,” Ms. Shalpa, 35, said in the middle of a frantic effort to distribute refugees among buses, parked in front of the first Russian railway station on the other side of the border.
On Friday, Mr. Putin ordered the government to pay $130 to every refugee, and the Russian region of Rostov, which has several crossing points with the separatist areas, declared a state of emergency.
By Saturday, several thousand people had fled the separatist regions of Ukraine and crossed into Russia.
As the separatists stirred upheaval in eastern Ukraine, the Russian missile tests, of three ballistic and cruise missiles, were also intended to send a different message, that a conflict could quickly escalate.
Mr. Putin watched the display from a Kremlin command center, accompanied by President Aleksandr G. Lukashenko of Belarus, which is considering letting Russia base some of its nuclear arsenal on its territory.
The test was technologically unremarkable, with videos issued by Moscow showing a fighter jet releasing a cruise missile from the air, a mobile-launch vehicle shooting off an intercontinental ballistic missile and a hypersonic sea-launched missile.
The Kremlin said the test was designed to show off Russia’s “triad” — launches from the ground, air, and sea — which mirrors the array of weapons in the American arsenal. Two of the three weapons were designed to evade U.S. missile defenses.
In Munich, Western leaders continued to insist that diplomacy was still possible while warning of serious consequences for Russia if it invaded.
Ms. Harris said in that case, the United States and its allies would target not only financial institutions and technology exports to Russia, but also “those who are complicit and those who aid and direct this unprovoked invasion.”
“Russia continues to claim it is ready for talks, while at the same time it narrows the avenues for diplomacy,” she said. “Their actions simply do not match their words.”
Similar warnings were uttered by Prime Minister Boris Johnson of Britain and the European Commission president, Ursula von der Leyen. She promised a serious package of financial and economic sanctions against Moscow in case of any aggression, which “may cost Russia a prosperous future.”
The new German chancellor, Olaf Scholz, said a Russian move into Ukraine would be a “grave mistake” that would prompt immediate and heavy “political, economic and strategic” consequences.
“Nothing justifies the deployment of well over 100,000 Russian soldiers around Ukraine,” he said. “No country should be another’s backyard.”
Even the Chinese foreign minister, Wang Yi, in a striking comment of some distancing from Russia, said that the sovereignty, independence and territorial integrity of every country should be safeguarded. “Ukraine is no exception,” he said in a virtual appearance at the Munich conference.
But President Volodymyr Zelensky of Ukraine , who flew to Munich for a few hours despite American concerns that he not leave his capital, Kyiv, impatiently pressed Western leaders to take stronger action now.
“What are you waiting for?” he asked. “We don’t need your sanctions after” the economy collapses and “parts of our country will be occupied.”
He also made clear that Ukraine would continue to seek membership in NATO, and blamed the West for not being honest about whether it really would welcome Ukraine into the alliance.
“We are told the doors are open,” he said. “But so far, the strangers are not allowed. If not all members are willing to see us, or all members do not want to see us there, be honest about it. Open doors are good, but we need open answers.”
Mr. Biden’s televised speech on Friday evening was the first time that the president had said that he now considered, based on intelligence and troop movements, that Mr. Putin had decided on a major invasion of Ukraine “in the coming week, in the coming days,” adding that “we believe that they will target Ukraine’s capital, Kyiv, a city of 2.8 million innocent people.”
The United States now says that Russia has as many as 190,000 troops in or near Ukraine, nearly twice as many as there were in January, according to an assessment made public on Friday by Michael Carpenter, the U.S. ambassador to the Organization for Security and Cooperation in Europe.
American officials said that Mr. Biden’s assessment was based in part on new intelligence showing that nearly half of the Russian forces had moved out of staging and into combat formation, and could launch a full-scale invasion within days.
And in recent days, researchers have seen the Russians put their surface-to-air missiles on alert, with the missile canisters pointing straight up into the air in firing position instead of the normal horizontal direction.
But Mr. Biden’s heightened sense of urgency was not immediately apparent in Kyiv, despite his having explicitly identified the capital city as a Russian target. The idea of Russian forces storming what is currently a calm and peaceful city was hard for many people there to imagine.
“Russia will do something,” said Sofiya Soyedka, 32, a Kyiv resident.
But invade Kyiv? “No way,” she said.
Reporting was contributed by Andrew E. Kramer from Severodonetsk, Ukraine; Roger Cohen, David E. Sanger and Katrin Bennhold from Munich; Marc Santora from Kyiv, Ukraine; Valerie Hopkins from Novoluhanske, Ukraine; Ivan Nechepurenko from Rostov-on-Don, Russia; and Julian E. Barnes and Eric Schmitt from Washington.