The accusation came out of the blue.
Maria Zakharova, the Russian Foreign Ministry's spokeswoman, made the dramatic claim last week that Montenegro was responsible for inflaming "anti-Russian hysteria" and for the "unacceptable treatment of Russians, who may expect provocations and detentions" while visiting that southern Balkan state.
The Montenegrin Foreign Ministry promptly responded by pointing to the absence of any reported incidents of Russian businessmen or tourists being harassed in Montenegro or experiencing any hostility from local residents.
"This is therefore nothing but manipulation and the continuation of a media war that Moscow has been waging against Montenegro, aimed at blocking its accession to NATO," the ministry said.
Moscow's warning to Russians follows reports in Russian state media that cast Montenegro as a country of "crime, minefields, and dirty beaches."
This marks a distinct change of tone toward a country long regarded by Russian authorities as an unobjectionable tourist destination, and many have been quick to link the shift to Montenegro's determination to join NATO.
Montenegro is indeed set this spring to become NATO's 29th member, marking the end of a long and often arduous road to accession. The government in Podgorica has had to face down a steady stream of rhetoric against NATO expansion from opponents both domestic and foreign, and an alleged coup attempt in October was seen by some as yet another attempt to change the political landscape and keep Montenegro away from Euro-Atlantic integration.
The court case surrounding that muddled affair is expected to be resolved by September, and the suspects include Montenegrin, Serbian, and Russian nationals.
But the warning to Russian citizens by their government made waves because the tourism season is approaching in Montenegro. Tourism is a major source of revenues, and former Foreign Minister Branko Lukovac told RFE/RL in Podgorica that interest in vacationing there remains high among Russians despite the media campaign in Russia.
Asked about the security of Russian citizens in Montenegro, a Podgorica correspondent for the Russian daily Kommersant told RFE/RL that he was unaware of any problem.
"If any Russian citizens in Montenegro had experienced some unpleasantness, it would have become public knowledge immediately, at least through social media," Gennady Sysoyev said.
Russian fans of Montenegro reacted with bewilderment on social media to Zakharova's comments, he added. "Hundreds were simply incredulous. Those who have spent time in Montenegro have never experienced any such treatment."
An "I was in Montenegro" Twitter hashtag (#ябылвчерногории) campaign has commenced on social media and attracted pics of some of the country's most scenic places...
...as well as videos, this one pretty polished:
Travel agencies are meanwhile busily booking vacations for Russians, who traditionally make up around one-third of all summer-holiday visitors to Montenegro.
A Montenegrin tourism-industry insider, Zarko Radulovic, predicts that the coming season will be Montenegro's best since it declared independence from Serbia 11 years ago, due in part to Russian customers.
"As long as they are not forbidden from doing so, Russians will keep returning to Montenegro. Since they are footing the bill for their own vacations, they -- and not the government -- will choose their destination, and many of them will choose to come here," he says. "It's not [Russian President Vladimir] Putin who pays for them, and he can't decide where they spend their leisure time."
Talking to RFE/RL in Podgorica, Radulovic -- who manages one of the most popular hotels on Montenegro's roughly 70 kilometers of Adriatic beachfront -- says he is optimistic that bad publicity in Russia won't have major adverse effects because so many Russians live in Montenegro and spread the good word among their compatriots.
"I can only welcome both in Montenegro," he adds, "NATO and Russian tourists."