Poland detained a Russian citizen accused by Warsaw of planning to kill a Ukrainian-American dual citizen in the Polish capital on Moscow's orders, Prime Minister Donald Tusk announced on Thursday.
Tusk told journalists the suspect had been arrested last Friday.
"He was inconvenient from the point of view of the Putin regime and at the last moment...we managed to prevent this execution," he added.
"This is the first situation of its kind in which someone, acting on Russian orders, decided to carry out an attack against an American citizen on the territory of another NATO country," he added.
Tusk said agents of the Polish Internal Security Agency (ABW) and police had arrested the suspect, with cooperation from American services.
"We have to accept the assumption that the Putin regime will try to eliminate people who are inconvenient for various reasons," Tusk said.
Warsaw, he added, "will likely come under similar pressure again."
Poland, a NATO and EU member state along the alliance's Eastern flank, has accused Russia of "sabotage" on several occasions since Moscow's full-scale invasion of Ukraine in 2022.
In June, Russian caricaturist and Putin critic Semyon Skrepetsky, whose real name was Robert Kuzovkov, was shot dead in eastern Poland. Tusk later called the killing a "political murder."
While last November, a railway line linking Warsaw to southeastern Poland was damaged by an explosion that Tusk called an "unprecedented act of sabotage."
Tusk said the line is "crucially important for delivering aid to Ukraine."
Several opponents of the Russian authorities have been victims of attacks abroad, including in the United Kingdom, Germany and Lithuania.
Moscow has always denied any involvement in these attacks.
