Poland’s prime minister appeared Wednesday to confirm the conclusions of Western intelligence officials who warned of a Russian plot to blow up a cargo plane over Western countries.

“I can only confirm that Russia planned acts of aerial terrorism, not only against Poland, but also against airlines around the world,” Prime Minister Donald Tusk said during a meeting with Ukrainian President Volodymyr Zelensky.

Mr. Tusk did not provide details, and it is not clear whether officials believe that Moscow continues to actively plan such action.

Officials first became aware of the plot over the summer, when incendiary devices planted at shipping hubs in Britain and Germany ignited fires that caused minimal damage. In November, four Western officials briefed on intelligence about the operation said the fires were part of a test of security measures carried out by Russia’s military intelligence service, known as the GRU.

The ultimate goal of the plot was not known, but intelligence agencies launched an investigation into whether the intent was to destroy aircraft on American or European runways or even blow up the aircraft in mid-air.

By fall, the White House had become so concerned that President Biden ordered his national security adviser and CIA director to warn top aides to Russian President Vladimir V. Putin that such a plot could provoke a strong response from the United States. Any act of sabotage that caused mass casualties would represent a serious escalation of the conflict between Moscow and Washington, and the United States would hold Russia responsible for “enabling terrorism,” a senior official told The New York Times.

While the Kremlin has denied that its agents were involved in the sabotage, Western officials say Moscow has ordered its intelligence services to find ways to bring the war in Ukraine, soon to enter its fourth year, into Europe and the United States.

Many sabotage plots attributed to Russia appear amateurish, intended more to annoy than to terrorize. In December, Estonian authorities released details of a group of GRU agents paid to smash the interior minister’s car windows and deface World War II monuments, and in France Russian agents have been linked to anti-Semitic graffiti spray-painted on walls.

But other episodes were more sinister. Fires broke out in weapons factories that supply Ukraine with weapons, as well as in buses and shopping centers. Critical telecommunication cables crossing the Baltic Sea were also cut, although it was difficult to definitively attribute them to a single country. Last year, two killers believed to have ties to Russia killed a Russian defector in southern Spain.

The sabotage campaign, officials said, is being led almost exclusively by the GRU, an agency that has carried out sabotage and assassination operations in Europe since before Putin’s 2022 invasion of Ukraine. Most notably, GRU operatives used a very powerful nerve agent in the attempted assassination of Sergei Skripal, a GRU defector living in Britain.

After Russia’s all-out invasion of Ukraine, the GRU’s activities in Europe weakened somewhat as European countries expelled operatives and restricted travel for Russians. But in the past year, the agency has figured out ways to revamp its operations. Officials say many acts of sabotage are carried out by hired proxies, sometimes recruited over the Internet. This is one of the reasons why operations have achieved limited results so far. But officials worry that recruiting people online to carry out such operations also increases the risk of dangerous and potentially deadly mistakes.

“The GRU in particular is on a permanent mission to wreak havoc on the streets of Britain and Europe,” warned Ken McCallum, director general of Britain’s Mi5, the country’s domestic intelligence service, in rare public statements last fall. “We saw arson, sabotage and more. Dangerous actions that are carried out with increasing recklessness.”