May 10 (UPI) -- A Montenegro court Thursday found 14 people including two suspected Russian agents guilty of plotting to overthrow the Balkan country's government in 2016 to prevent it from joining NATO.
Eduard Shishmakov and Vladimir Popov, operatives with the Russian military intelligence agency formerly called G.R.U., were convicted of attempted terrorism and having created a criminal organization. Shishmakov was also convicted of inciting acts against the constitution and safety of Montenegro, the United Kingdom confirmed.
Shishmakov was sentenced to 15 years in prison while Popov was sentenced to 12 years, Montenegro's CDM reported.
They were tried in absentia and are believed to be in Russia.
Judge Susana Mugosa said the two Russians "knowingly tried to terrorize Montenegrins, attack others, threaten and hurt basic constitutional and social structures," the New York Times reported.
Two leaders of the left-wing Democratic Front opposition party Andrija Mandic and Milan Knezevic were each sentenced to five years in prison for coordinating with the two Russians. Neither was present during sentencing.
Mandic and Knezevic said they will appeal the verdict, Balkan Insight reported.
"This is a breaking point for Montenegro," Mandic said in a press conference. "We don't accept arrests."
He then accused Montenegro President Milo Dukanovic and his brother, Aleksander Dukanovic, of lying that there was an attempted coup while urging Serbia to speak out against their convictions.
"We Serbs in Montenegro will not be slaves," Knezevic said.
Former commander of an elite Serbian police unit Bratislav Dikic, who was arrested in October, was sentenced to eight years in prison.
The other defendants received sentences ranging from one to eight years.
According to the verdict, the group had planned to assassinate then-Prime Minister Milo Dukanovic on election day Oct. 16, 2016, and install a pro-Russian, anti-NATO leader.
The coup was thwarted by police after receiving a tip by Western spy organizations, Al Jazeera reported.
Russia has denied any involvement in the attempted coup.
The U.S. embassy in the capital of Podgorica said the verdict was a "historic day for the rule of law in Montenegro."
"The open and transparent trial represents an important step forward for the rule of law and sends a strong message about the unacceptability of efforts to undermine democracy," the office said in a tweet.
The 2016 election was largely seen as a referendum on joining NATO, which Montenegro had agreed to but not formally ratified.
Some 20 Serbian nationalists were arrested on the eve of the election with the 14 convicted Thursday being charged of plotting the overthrow of the country.
Montenegro joined NATO June 5, 2017, some 11 years after it gained independence.
The United Kingdom said the failed coup was "one of the most outrageous examples of Russia's attempts to undermine European democracy."
"The G.R.U.'s brazen attempt to interfere with Montenegro's national elections and undermine Montenegro's application to join NATO is yet another example of destabilizing and aggressive Russian behavior over the last decade," U.K.'s Foreign Secretary Jeremy Hunt said.
The guilty verdicts were the product of "unprecedented transparency" while Russia's claims the two men were researching Russian military in the region during the first world war for an article "were proven to be absurd."
He then demanded that Russia stop attacking other nations' democratic process while calling on Moscow to uphold the security of Europe and fulfil its responsibilities to the United Nations Security Council.
The U.S. State Department echoed the U.K.'s message, calling the verdicts a "clear victory for the rule of law" while "laying bare Russia's brazen attempt to undermine the sovereignty of an independent European nation."
"The United States is proud to count Montenegro as an ally and will continue to support Montenegro in its efforts to strengthen the rule of law, protect media freedom and advance other reforms needed to join the European Union," State Department spokeswoman Morgan Ortagus said in a statement.