Russia plotted to assassinate Montenegro's prime minister and overthrow its government in a bid to sabotage the country's plan to join Nato, it has been reported.

Citing senior Whitehall sources, The Sunday Telegraph reported the election-day plot - which involved attacking the tiny eastern European country's parliament - was directed by Russian intelligence officers with the support of Moscow.

However, no such coup occurred as the plot to kill Milo Đukanović was reportedly foiled hours before it was due to be carried out.

The allegation comes a day after Sergey Lavrov, Russia’s Foreign Minister, criticised Nato as a “Cold War institution” whose expansion had led to unprecedented tensions in Europe over the past thirty years.

According to The Sunday Telegraph, the planned coup - scheduled for October 16, 2016 - was one of the strongest recent examples of an increasingly aggressive campaign of interference in Western affairs by Russia.

The Sunday Telegraph also reported that Foreign Secretary Boris Johnson, and his US counterpart, Rex Tillerson, discussed the issue last week at their first face-to-face meeting.

The newspaper also reported Interpol is now hunting two Russians who the Montenegrin government claims are intelligence officers who hatched the plot.

It is claimed the pair spent months overseeing the recruitment and equipping of a small force of Serbian nationalists to attack the parliament building, disguised as police, and kill the then-prime minister.

Mr Đukanović was succeeded as prime minister by Duško Marković.

Motenegro's current Prime Minister Duško Marković. Credit: AP

The Kremlin has strongly denied any involvement in a plot, while the Montenegrin special prosecutor, Milivoje Katnic, has stopped short of alleging Moscow's involvement in a plot, instead reportedly blamed on Russian nationalists.

The Sunday Telegraph reported British and American intelligence agencies called in to help the Montenegrin authorities unravel the alleged conspiracy are thought to have gathered evidence of high-level Russian complicity.

The front-page article continued that encrypted phone calls, email traffic and testimony from plotters-turned-informants are now part of the criminal investigation of 21 conspirators accused of terrorism and preparing acts against the constitutional order of Montenegro.

Predrag Bosković, Montenegro's defence minister, told The Sunday Telegraph there is “not any doubt” that the plot was financed and organised by Russian intelligence officers alongside local radicals.

Sources reportedly said the plot appeared to have been constructed so it was deniable and could be blamed on rogue Russian agents and nationalists, adding evidence showed it was inconceivable it did not have high-level backing.

One source is reported to have said: “You are talking about a plot to disrupt or take over a government in some way. You can’t imagine that there wasn’t some kind of approval process.”

Nemanja Ristic, one of the alleged plotters, was recently photographed standing next to Sergei Lavrov as he visited Serbia.

Nemanja Ristic (far left) pictured with Russian Foreign Minister Sergey Lavrov in Serbia. Credit: AP

Earlier this month, Defence Secretary Michael Fallon warned Russia is "weaponising misinformation" in an effort to destabilise the West.

In a no-holds-barred speech, Sir Michael accused Moscow of using cyber tools to "disrupt critical infrastructure and disable democratic machinery" in a series of attacks on western countries.

October's alleged plot followed repeated warnings from Moscow that Montenegro should abandon plans to become Nato's 29th member later this year.

Moscow has been keen for the country of 620,000 people to remain inside its sphere of influence, or at least neutral, and has in the past lobbied hard for naval access to its Adriatic ports.

In the months running up to the alleged coup, the Kremlin is suspected of pouring millions of pounds into a pro-Russian election campaign run by the country’s main opposition bloc, the Democratic Front.

Mr Katnic reportedly said the plotters would have mingled with Democratic Front protestors outside the parliament building in the country’s capital, Podgorica, as the election results were announced.

At an appointed sign, the conspirators would reportedly have forced their way inside, and in the confusion, colleagues dressed in police uniforms would have also opened fire on the crowd “so that citizens would think that the official police are shooting at them”.

“Had it been executed, such a scenario would have had an unforeseeable consequence," they were quoted as saying.

Mr Katnic reportedly said he had “obtained evidence that the plan was not only to deprive of liberty, but also to deprive of life the then Prime Minister.”