The Polish Foreign Ministry said it had received scant information on the Night Wolves, a group with ties to Vladimir V. Putin, before a ride from Moscow to Berlin.
For more than a year, since the Ukraine conflict erupted, European nations have been having an argument among themselves about how to respond to Russia.
The director of the F.B.I., James B. Comey, told the Polish ambassador to the United States that he regretted recent remarks that Polish officials had said amounted to an accusation of complicity in the Holocaust.
Tensions continued to simmer over comments last week by James B. Comey, the F.B.I. director, that suggested that Poles were Nazi accomplices during the Holocaust.