Story highlights Montenegro officials say they have evidence of Russia's involvement in attempted coup

Russia denies the allegation

(CNN) Montenegro's chief special prosecutor has told a local TV station authorities believe Russian security services were involved in a plot to kill the country's then-prime minister and overthrow the government last October.

Milivoje Katnic said Montenegro officials have evidence that Russia's Federal Security Service was involved in the failed coup, according to his statements Sunday on Atlas TV. The allegation drew an immediate rebuke and denial from Russian officials.

Katnic said the plot was an attempt to stop Montenegro from joining the North Atlantic Treaty Organization, or NATO.

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"Behind these events are nationalist structures from Russia, but we now know that certain Russian state authorities were involved also on a certain level," Katnic said.

Katnic said the alleged mastermind behind the failed coup was a man named Eduard Sismakov, who is a former deputy Russian military attaché in Poland. Sismakov was deported to Russia for espionage in 2014, according to the prosecutor.

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