An explosive-laden drone at a German airport. A strike on a passenger train near the Polish border. A rush of warnings about more chaos to come.

If President Vladimir V. Putin of Russia was hoping to heap pressure on Ukraine’s closest allies, he’s succeeded with a series of provocations that Western officials have blamed on Russia and said could put citizens of NATO countries in danger. The question is how Europe responds.

In the past week, European leaders have spoken with uncommon urgency about Russia’s shadow war. Prime Minister Donald Tusk of Poland, citing unspecified intelligence, said Moscow may be planning attacks in Europe. “No one is safe,” President Emmanuel Macron of France cautioned. The British prime minister, Andy Burnham, told the U.N. General Assembly that his country faced an “industrial-scale assault” in terms of information warfare.

In an assessment released on Thursday, the Danish government’s defense intelligence service concluded that Russia would increase its threats to NATO nations, “with greater consequences for the targeted countries than in the past.” The theory is that Mr. Putin, bogged down on the battlefield, is stepping up attacks on Ukraine’s supporters, hoping to sow fear and panic and, ultimately, weaken their support for Kyiv. It won’t work, says the NATO secretary, Mark Rutte. “Russia wants us to stop helping Ukraine,” he said in a recent address. “Their actions will only lead us to do more for Ukraine.” For years, officials and experts have accused Mr. Putin of targeting Europe with hybrid attacks — hostile actions that are designed to evade culpability, and that generally stop just short of inflicting enough damage to trigger a forceful response. What has changed, according to Charlie Edwards, a former British intelligence official now at the International Institute for Strategic Studies, is the “potential lethality and operational ambition of Russian sabotage operations.” German investigators this month concluded that Russian operatives sent a drone equipped with military-grade explosives to Leipzig/Halle Airport in eastern Germany over the summer.

Had the drone exploded, officials said, it would have caused significant damage and possibly killed people. Earlier this month, a Russian drone smashed into a passenger train in western Ukraine, perilously close to the Polish border, as foreign visitors were leaving a diplomatic conference in Kyiv. It was widely seen as a warning to Ukraine’s allies. “We have to be prepared more, and we have to understand that this activity is now becoming almost ever-present,” the European Union’s top military adviser, Gen.

Sean Clancy of Ireland, said in an interview. On Wednesday, President Volodymyr Zelensky of Ukraine warned that Russia’s war would continue to spread unless allies responded. “The more freedom Putin has to act, the more dangerous the world becomes for everyone else,” he said in a speech in New York. The Kremlin has consistently denied involvement in hybrid activities.

Russia’s foreign minister, Sergey V. Lavrov, has pointed instead to what he calls Western “large-scale political, economic, and coercive measures, including sanctions.” “This is the hybrid war,” he said in a recent speech. What’s driving Russia? Western security officials say they have seen no sign of Russia preparing for a conventional war with NATO.

Rather, officials say, Mr. Putin and his overstretched forces are looking for ways to undermine Kyiv and its allies. “Russia doesn’t have the capacity to challenge NATO” right now, Baiba Braze, the minister of foreign affairs for Latvia, said in an interview in Riga. “They cannot move the front,” she said. “They are not gaining territory.” What Moscow can do, though, is continue to pursue relatively low-cost hybrid attacks. That has included sending drones into NATO territory to surveil military bases and disrupt commercial air traffic, jamming navigation systems of passenger planes, and hacking into energy grids and dams. Last week, a Russian-linked hacker group claimed responsibility for disabling traffic lights in multiple cities across Poland, causing gridlock and raising fears of broader infrastructure attacks.

In France, officials reported a surge in cyber intrusions targeting transportation networks and energy firms, which they attributed to Russian state-sponsored actors. The European Union has responded with new sanctions and increased cyber defense cooperation, but analysts say the pace of escalation may outstrip current countermeasures. As hybrid tactics grow more sophisticated and frequent, Europe faces the challenge of balancing deterrence with restraint — all while trying to prevent the war in Ukraine from spreading beyond its borders.