SARAJEVO (Reuters) - NATO enlargement to take in members from the Balkan countries is undermining security and stability in the region, a senior Russian parliamentarian said on Monday.

Valentina Matviyenko, speaking in the upper house of Bosnia’s parliament, singled out neighboring Montenegro which recently became a NATO member, but also criticized Macedonia’s aspirations to join the U.S.-led military alliance.

“Montenegro’s joining NATO against the will practically of half of its citizens has become the harshest violation of the basic principles of modern democracy,” Matviyenko, speaker of the Russian parliament’s upper house, said.

Macedonia was also trying the “same dangerous experiment”, she said, adding: “This step is leading only towards further destabilization of the situation in the region. It undermines the system of European security.”

Western governments see NATO and European Union membership as the best way of preserving the peace and stability in the Balkans after a decade of wars with the break-up of Yugoslavia in the 1990s.

Montenegro joined the military alliance last year and hopes to join the European Union in 2025 at the same time as Serbia. Croatia, another former Yugoslav republic, joined in April 2009.

Both Montenegro and Macedonia have expelled Russian diplomats over the nerve toxin poisoning of a former Russian double agent. The British government has blamed the attack on Moscow, though Russia denies any involvement. The Kremlin then expelled a Montenegrin diplomat and summoned embassy officials from Macedonia.

Montenegrin prosecutors say a group of Serb nationalists and Russian agents plotted to kill then Prime Minister Milo Djukanovic during a coup attempt at the 2016 election to prevent Montenegro from joining NATO. The Kremlin dismissed such allegations as absurd.

Bosnia hopes to activate a NATO pre-accession Membership Action Plan but its plans for the membership of the alliance are blocked by Bosnian Serbs who see Russia as their main ally.

Last month, Bosnia’s security agencies banned leaders of the Russian Night Wolves motorcycle club from entering the country because of security concerns. The club is under U.S. sanctions for its role in a pro-Russian separatist insurgency in Ukraine.