Poland said Friday it arrested a Russian ice hockey player on suspicion of having spied for Moscow while playing for a Polish club, promptingRussiato protest and demand an "immediate" explanation.Relations between Warsaw and Moscow have been hostile historically but have reached new lows during the Russian invasion of Ukraine, with Poland being one of Kyiv's staunchest allies.Warsaw said the man was the fourteenth person arrested in what it called a spy ring taking orders from Moscow."All of them were identified as foreigners from beyond the eastern border of the Republic of Poland," Warsaw's ABW secret services said, without clarifying if all of the suspects were Russian citizens."The entire group was used by the Russians to conduct intelligence activities, including monitoring railway routes, as well as spreading propaganda against NATO, Poland and the policies of the Polish government," it added."The suspects were also preparing sabotage acts on behalf of Russian intelligence."Poland did not name the arrested man, saying only that he is a "professional athlete from a first-division hockey club."It said he was arrested on June 11 in the southern Silesian region and had lived in Poland since 2021.Russian state media identified the man as Maxim Sergeyev, who played for Zaglebie Sosnowiec in the southwestern Polish city of Sosnowiec.The website of Polish hockey teams listed Sergeyev as being 20 years old and from Reutov, a town outside Moscow.Polish authorities said they had charged the man with espionage and that he will remain in custody for three months.The Russian Foreign Ministry said it had expressed a "strong protest" to Poland."We demand that the Russian side be immediately provided with comprehensive explanation."It added that the arrested Russian national will be provided with "all the necessary help."