A Vladimir Putin-backed motorcycle club called Night Wolves - sometimes portrayed as Russia's Hells Angels - has triggered a protest in Poland.
The bikers plan to ride through Poland on a trip to celebrate the 70th anniversary of the Soviet victory over the Nazis, ending in Berlin on 9 May.
The Night Wolves draw support from the Kremlin and the Russian Orthodox Church. They plan to ride their Harley-Davidsons on a 6,000km (3,720-mile) road trip through Russia, Belarus, Poland, the Czech Republic, Slovakia and Austria, before reaching Berlin.
The bike rally will include other Russian motorcycle clubs, and is due to start on 25 April. They plan to stop at historical sites en route, including Auschwitz in southern Poland.
It is the Night Wolves' connection to Russia's President Putin that has angered some Poles. Some Polish newspapers printed photographs on Tuesday of Mr Putin riding an enormous three-wheel Harley-Davidson Lehman Trike with them in Crimea in July 2010. The club supported calls for the Ukrainian peninsula's return to Russia - which happened last year.
'Warning for Poles'
More than 10,000 Poles have protested against the Night Wolves entering the country on a Facebook page called "No to the Russian bandits' ride through Poland".
The page is co-hosted by Jarek Podworski, a biker from Krakow, who says the Night Wolves support the Moscow-backed separatist fighters in Ukraine.
"Is this ride across Poland a warning for Poles or also the beginning of Russian aggression?" the page reads.
"We hope that our motorcycle brothers, regardless of their club, will put them in their place. We will not be scared. Block their ride through Poland! They have no right to cross the Polish border!" it said.
A snap opinion poll conducted for the TVN channel found 52% of respondents opposing the rally.
Polish Prime Minister Ewa Kopacz described the planned ride as a "provocation", saying a final decision on whether the bikers should be allowed into the country would be taken by the border guard.
The bikers' leaders had not applied for visas for either Poland or Germany, she added.
The Polish government has been sharply critical of Russia's annexation of Crimea and its involvement in eastern Ukraine.
Pawel Kowal, a former deputy foreign minister, said the government should work on legal obstacles to prevent the bikers entering Poland.
"This is playing with Poland, and Poland should clearly state that it sees these intentions," he said.
However, other politicians disagreed. Leszek Miller, a former communist who leads the left-wing opposition SLD party, cited the case of Polish bikers who ride to Katyn in western Russia to remember the murder of more than 21,000 Polish officers by the Soviet secret police in 1940.
"If Poland were to decide on some restrictions the Russians could do the same to our motorcyclists who ride to Katyn," he said.
Another Facebook page in favour of the Russian bikers' plans has been liked by more than 1,000 people, including some club members who ride to Katyn.