A Kremlin-linked biker gang sanctioned by the U.S. is starting a nine-day tour of the Balkans this month.
World leaders, designer labels, artists and more unveiled their tributes to Russian President Vladimir Putin for his 65th birthday.
Russia's president has not declared owning any motorcycle in his official records.
The group has vowed to bring "several hundred" riders to Berlin by May 9.
The former champion became a Russian citizen last month.
"The border guards are aware that there might be people with visas that are valid but have actually been annulled."
Anna Komarova, spokeswoman for the Night Wolves in Moscow, said that the group is not going to change its plans.
The bikers are riding to Berlin to celebrate the Red Army's victory over the city in WWII.