Russia has been plotting to place incendiary devices on cargo planes in Europe and even performed a test run this summer, setting off fires at shipping hubs in Britain and Germany, according to four Western officials briefed on intelligence about the operation.

The effort represents a potentially significant escalation of the Kremlin’s sabotage operations against Western adversaries.

The goal of the plot, orchestrated by Russia’s military intelligence agency, the GRU, is not entirely clear, according to two of the officials, all of whom spoke on condition of anonymity to discuss sensitive intelligence matters. It could have been what ultimately occurred: to set fires with incendiary devices placed at logistics hubs belonging to the package shipping company DHL, perhaps meant to instill fear or deliver a warning.

But Western intelligence agencies are also investigating whether Russia intended something more ambitious, and menacing, such as destroying planes on American runways, setting off bombs at U.S. warehouses or even blowing up aircraft midair. Officials said that both the U.S. and its European allies were potential targets of the Russian plot.

The operation is an effort by Russian President Vladimir Putin to inflict damage on the West for its support of Ukraine’s military, officials said. The Kremlin’s goal appears to be to shake Western backing for Ukraine or, failing that, exact a price for it.

In the first two years of the war with Ukraine, the Kremlin largely avoided directly provoking Kyiv’s allies, particularly those belonging to NATO, officials said, fearful of a dangerous escalation. Today, any such reticence appears to have dissolved, they said.

“Hostile activity carried out on behalf of the Russian Federation is increasingly taking the form of terrorist activities,” Poland’s domestic intelligence service said in a communiqué published last month.

The Kremlin has denied that its agents engage in sabotage.

What is known

The incendiary devices were planted at DHL shipping hubs in Leipzig, Germany, and Birmingham, England, the Western officials said. The fires caused minimal damage and no injuries, they said, but the blazes raised the frightening specter of bombs potentially being loaded on aircraft.

The Wall Street Journal described details of the plot on Monday.

In a statement, DHL, whose global headquarters are in Germany, confirmed “two recent incidents involving shipments in our network.”

“We are fully cooperating with the relevant authorities to protect our people, our network and our customers’ shipments,” the statement said.

Last month, Polish authorities announced the arrests of four suspects involved in planting the incendiary devices. The country’s National Prosecutor’s Office said the plot had been part of a test run with the ultimate goal of putting explosive devices on planes bound for the United States and Canada, though the Western officials could not confirm this was the intent.

American targets?

It is possible that Russia wanted the option of eventually blowing up cargo planes flying to or over America. But the officials briefed on the intelligence said that would be a stark change from Russia’s current strategy of “horizontal escalation,” in which Moscow seeks to carefully manage its responses to allied support to Ukraine. Blowing up a plane over the United States, which would revive memories of the Sept. 11, 2001, attacks, would provoke a strong retaliation from Washington, something Russia has wanted to avoid.

But Western intelligence agencies have not ruled out the possibility that Moscow wants at least the option of carrying out such a provocative attack; that would be especially true if the United States enables Ukraine to strike deeper into Russia or provides Kyiv with more powerful weaponry, something the Biden administration has so far resisted.

Over the last several months, the Transportation Security Administration has added “security measures for U.S. aircraft operators and foreign air carriers regarding certain cargo shipments bound for the United States,” a spokesperson for the agency said in a statement to the Times.

A U.S. government official, speaking on condition of anonymity, said at this time there was “no current active threat targeting U.S.-bound flights.”

The sabotage campaign is being waged almost exclusively by the GRU, officials said. It is an agency that European security officials have long been familiar with. In 2018, operatives from the agency used a highly potent nerve agent in the attempted assassination of Sergei Skripal, a GRU defector who was living in Britain.

The agency was behind a similar assassination attempt against a Bulgarian arms manufacturer, as well as explosions at weapons plants in the Czech Republic and a thwarted coup in Montenegro, according to Western security officials.

After Russia’s full-scale invasion of Ukraine, the GRU’s activities in Europe abated somewhat as European countries expelled operatives and limited travel for Russians. But in the past year, the agency has figured out ways to restore its operations.

“The GRU in particular is on a sustained mission to generate mayhem on British and European streets,” Ken McCallum, the director general of Britain’s Mi5, the country’s domestic intelligence service, warned in rare public remarks last month. “We’ve seen arson, sabotage and more. Dangerous actions conducted with increasing recklessness.”