Kyiv has hit out at German police after officers in Berlin confiscated a huge Ukrainian flag.
It was unfurled at the Soviet Memorial in the German capital on the eve of Russia's Victory Day, which marks its defeat of Nazi Germany during World War II.
Officials in Germany said neither Russian nor Ukrainian flags were allowed to ensure commemorations stayed peaceful.
But Ukraine's foreign minister, Dmytro Kouleba, took to Twitter to protest.
"Berlin made a mistake by banning Ukrainian symbols. It is deeply wrong to treat them on an equal footing with Russian symbols. It is an attack on all those who are currently defending Europe and Germany against Russian aggression."
Fearing scuffles, in particular from pro-Russian activists, Berlin police announced on Friday a ban on displaying flags or military symbols on about fifteen sites in the German capital during the commemorations of the end of World War II.
"To keep the peaceful and dignified commemoration in the foreground, our colleagues ensured that a Ukrainian flag approximately 25 meters long was rolled up" after being unfurled, Berlin police tweeted.
This decision caused an outcry, especially in the Ukrainian community.
Ukraine's ambassador to Germany, Andrij Melnyk, called the decision "scandalous" and "a slap in the face to Ukraine".
Renowned for not mincing words for German leaders, the diplomat laid a wreath of flowers in the blue and yellow colours of his country in the morning in front of the Soviet Memorial, in the heart of Berlin.
Despite a heavy police presence, protesters chanting "Melnyk out!" gathered near the Memorial, while others, pro-Ukrainians, shouted "Slava Ukraini" ("Glory to Ukraine" in Ukrainian).
This monument, located on the edge of Tiergarten Park, not far from the Brandenburg Gate, celebrates the memory of the 80,000 Soviet soldiers killed during the Battle of Berlin before the surrender of Nazi Germany on May 8, 1945.
Earlier thousands of people turned out in the German city of Cologne, taking part in rival demonstrations in support of Russia and in support of Ukraine.
About 1,000 people gathered to protest against arms deliveries to Kyiv and to show solidarity with Russian President Vladimir Putin.
However, a pro-Ukraine demonstration attracted significantly more participants.
Police were deployed to prevent clashes between the two groups.
Relations between Berlin and Kyiv have been strained by the war in Ukraine, with some arguing that Germany has not done enough to support them.