Poland on Thursday said it had detained nine foreigners accused of spying for Russia and preparing operations to disrupt the flow of western arms into neighbouring Ukraine. Mariusz Kaminski, the Polish interior minister, announced the dismantling of what he said was a major Russia espionage network a day after a visit to Warsaw, Poland’s capital, by the CIA director, William J. Burns, who has played a key role in coordinating the delivery of western-supplied arms to Ukraine by train and road from Poland.

“The suspects conducted intelligence activities against Poland and prepared acts of sabotage at the request of Russian intelligence,” Kaminski told journalists in Warsaw.

The planned sabotage, he said, was “aimed at paralysing the supply of equipment, weapons and aid to Ukraine”.

Poland, a stalwart ally of the US and one of Europe’s most robust supporters of Ukraine, is the main transit route for weapons and ammunition provided by the US and other countries to help Ukraine defend itself against Russia’s military onslaught.