Russia’s failed drone attack on a German airport was part of a dangerous pattern of escalation that, experts and officials said, risks sparking an open confrontation with NATO — whether the Kremlin wants it or not.

German officials declared this week that the Russian state was behind the attack, in which one explosive drone hit a parked Ukrainian cargo plane and another appeared to collide with a plane taking off. Both drones failed to detonate. If successful, the attack could have killed or maimed people and led to unpredictable consequences, officials said.

It was the most dramatic in a spate of such attacks that includes plots to place incendiary devices aboard DHL cargo planes, blow up railroad tracks in Poland, and burn down warehouses and shopping centers all over Europe.

Such attacks began occurring shortly after Russia launched its full-scale invasion of Ukraine in 2022, part of an effort by President Vladimir V. Putin to bring the war to the West. But they have recently increased in frequency and intensity, Western security officials said. The attacks, along with recent reports citing Western intelligence services suggesting Russia could be planning some kind of military incursion or provocation along NATO’s eastern flank, have frazzled Europe and left officials there casting about for solutions.

“Europeans are faced with the hard truth that this is the new normal,” Ursula von der Leyen, president of the European Union’s executive arm, said on Wednesday. “We have to step up, and that means being ready to respond to Russia’s recklessness better and faster.”

The uptick in attacks appears to be driven in part by Mr. Putin’s frustration with the situation on the battlefield, experts said. Progress is slow and casualties are enormous, while Russia’s economy has been strained by a Ukrainian campaign of long-range strikes against e-commerce warehouses, oil refineries and military logistics hubs. In Mr. Putin’s mind, Russia is not just at war with Ukraine, experts said. It is also battling what he calls the “collective West” that he blames for providing the weapons, intelligence and technologies that have kept the Ukrainians in the fight.

Mr. Putin has always denied Russia’s involvement in European sabotage and suggested that the German authorities had planted evidence of Russia’s involvement in the Leipzig attack. But he referred to the West this week as “the sharks of imperialism” and suggested Russia’s enemies would get what they deserved.

“If anyone tries to drag us down the food chain and gobble us up, devour us, they might get a punch in the teeth,” Mr. Putin said at a news conference. “And Russia is ready to do this, despite the rapidly growing appetites and teeth of these sharks.”

The German authorities also opened investigations into possible sabotage attacks on a defense contractor in Munich and two electrical substations; a fire erupted at a drone factory in Poland that officials said was most likely caused by sabotage; and Denmark’s intelligence service said Russia was recruiting Danes to attack defense firms.

That was only this week.

“Russia is both planning and carrying out acts of sabotage against defense companies and the defense industry in Europe,” the Danish intelligence service, PET, said in a statement. “Russian intelligence services are actively preparing acts of sabotage directed at the defense industry in Denmark.”

No one has been killed or seriously injured in the attacks, but any bloodshed would present a profound crisis for NATO, which was created to deter and fight a land invasion and lacks the tools to respond to a slowly escalating conflict. Already it has struggled with how to adequately respond to Russia’s aggression.

“Russia has gotten pretty lucky,” said Julianne Smith, the former U.S. ambassador to NATO during the Biden administration. “At some point, it is going to go off the rails and somebody is going to get hurt and it’s going to present a different dilemma for the alliance.”

In response to the attack in Leipzig, Germany announced the closure of a diplomatic mission and additional travel restrictions on Russians, among other measures. Publicly accusing Russia in connection with such activities is rare, in part because it can be hard to draw a direct line between the perpetrators and the Russian state.

Alexander Dobrindt, Germany’s interior minister, said Tuesday that investigators had proof that agents who controlled the drones were working “on behalf of Russian state entities.”

Confronting such attacks has proved difficult in particular for the North Atlantic Treaty Organization, which was conceived as a deterrent to invasion by the Soviet Union. So far, Russia’s actions have fallen short of that.

There is a question of how far Mr. Putin will go, particularly whether he will try to directly test Article 5, NATO’s central tenet. It states that an attack on one alliance member is an attack against all.

Few Western intelligence officials consider an imminent attack on a NATO member probable, certainly not one involving Russian ground forces, which are bogged down in Ukraine. But in the face of Western involvement in Ukraine, Mr. Putin may feel he has no choice but to bring the fight to Europe in some limited way, experts said.

“I don’t think they want a third world war, but they have to demonstrate to everyone that it is not the time to mess with them,” said Piotr Krawczyk, the former director of Poland’s foreign intelligence service.

There is little that NATO’s member countries can overtly do to punish Russia for the sabotage attacks, beyond imposing sanctions and expelling diplomats.

But a number of covert responses are open to Western countries, including increasing intelligence support to Ukraine, conducting cyberattacks and undermining Russian interests in other parts of the world. In August, the German government passed draft legislation to authorize its intelligence services to carry out active measures like sabotage and cyberattacks. If approved by the parliament, the agencies would gain that power for the first time in Germany’s postwar history.

The secret nature of such responses makes it difficult to assess their effectiveness, though Russia’s increase in attacks is a sign that the West’s efforts are falling short.

“Because they have not been adequately deterred and Moscow has not paid a price, Putin is interpreting that as a signal to keep going,” said Ms. Smith, the former ambassador.

Another challenge for NATO is keeping its 32 member countries aligned. After Germany’s announcement this week, a chorus of allies voiced support and solidarity, including the American ambassador to NATO, Matthew G. Whitaker. Notably, though, his statement did not mention Russia by name. By contrast, a statement by Prime Minister Andy Burnham of Britain named Russia three times.

The omission was an example of the failure by the Trump administration to hold the Kremlin accountable. Since taking office last year, Mr. Trump has occasionally dangled the possibility of imposing costs on Mr. Putin’s transgressions, but he has rarely followed through.

Last week at NATO headquarters, Elbridge Colby, a senior Pentagon official, also omitted any mention of Russia while pushing European countries to take the lead in supporting Ukraine, part of an effort to reduce U.S. military presence on the continent. And on Wednesday, Treasury Secretary Scott Bessent blamed Ukraine for high energy prices dragging down the global economy, citing its attacks on Russia’s oil industry. He did not mention that Russia started the war and has relentlessly targeted Ukraine’s civilian infrastructure.

It is the threat of a united response, Western officials believe, that keeps the Kremlin in check. And it is that unity that Mr. Putin seems to be testing with each new attack.

For now, Western officials insist that NATO retains its deterrent effect, though the ambivalence of the Trump administration has created uncertainty about whether it will continue to.

“Our assessment is that Vladimir Putin currently understands both what Article 5 means and what its actual consequences would be,” Kaupo Rosin, the head of Estonia’s Foreign Intelligence Service, said in an interview this week with a local news outlet.

“Our main concern, however, is the future,” he said. “We have to ensure that six months, one year, or five years from now, Russia still has the same understanding that NATO deterrence works.”

Steven Erlanger contributed reporting from Berlin, and Koba Ryckewaert from Brussels.