PODGORICA, Montenegro (AP) — Montenegro's special prosecutor has accused Russia and its secret service operatives of plotting a coup attempt that included plans to kill the small Balkan country's former prime minister, Milo Djukanovic.

Prosecutor Milivoje Katnic says that an investigation into the alleged plot last October to overthrow Montenegro's government and prevent it from joining NATO has shown "that Russian state bodies were involved at a certain level."

Russian officials vehemently denied the claim on Monday.

Katnic told Prva TV late Sunday that Eduard Shishmakov, an alleged Russian military spy, was the main coordinator of the plot.

Katnic says Shishmakov was deputy Russian military attaché in Poland before being expelled for espionage in 2014.

Some 20 people, mostly Serbian citizens, have been arrested in Montenegro over the alleged plot.