BERLIN — European and U.S. intelligence officials believe Russia is behind a plan that would ultimately place incendiary devices on planes to North America through air cargo shipments, according to people familiar with the matter.Authorities are taking the incidents seriously, and intelligence agencies are expecting Moscow to try and stage similar acts of sabotage in the future, one of the people said. They asked not to be named discussing the intelligence matter.Poland’s National Prosecutor’s Office has said in a statement on its website that it’s investigating the alleged involvement of a foreign intelligence service in sabotage activities on the territory of Poland and other European Union members states and the U.K. but didn’t specify Russia as the perpetrator. The Wall Street Journal reported earlier Monday on Moscow’s alleged goal of ultimately targeting the U.S.Poland’s interior minister said the efforts fit Russia’s pattern.“The year 2024 brought various acts of sabotage in Poland and other European countries,” Tomasz Siemoniak said Monday. “Our intelligence services and prosecutors have no doubt that Russian clients are behind this. The attempts to place explosives into courier shipments fit into the logic of Russian sabotage and do raise the threat up to a new level.”As part of the probe launched on Aug. 5, authorities have arrested four people linked to a sabotage group, whose activities included sending parcels containing camouflaged explosives and dangerous materials via courier companies to countries in the EU and the U.K.The parcels would ignite or detonate during land or air transport. “The group’s goal was to test the transfer channel for this type of shipments, which were ultimately to be sent to the U.S. and Canada,” according to the statement.Alexa Lopez, a spokeswoman for the US Transportation Security Administration, said in a statement that “over the past several months, as part of a multilayered security approach, TSA worked with industry partners to put additional security measures for U.S. aircraft operators and foreign air carriers regarding certain cargo shipments bound for the United States.”Governments across Europe have been raising alarm over a growing threat of Russiasponsored acts of sabotage and destabilization since the Kremlin launched its full-scale invasion of Ukraine more than two and a half years ago. Russia has repeatedly denied involvement in such efforts.Earlier this year, the U.S. warned its allies that Russia is targeting cargo shipping companies as it seeks to disrupt Ukraine’s partners, according to people familiar with the matter.