Protesters have targeted Berlin's State Opera for refusing to cancel Russian opera singer Anna Netrebko's first performance there since the 2022 war.
Chanting "shame", they accused the soprano of failing to condemn Vladimir Putin for Russia's invasion of Ukraine.
Berlin's mayor, its senator for culture and Ukraine's German ambassador have all criticised the opera for allowing the singer to return to its stage.
Ms Netrebko has criticised the war and argues she met Mr Putin a few times.
However, only a year before the invasion she celebrated her 50th birthday with a gala performance at the Kremlin and she has been shunned by opera houses in the US and elsewhere in Europe.
In the weeks leading up to her sold-out appearance as Lady Macbeth in Giuseppe Verdi's opera Macbeth, 37,000 people signed a petition demanding the role be given to someone else.
But the Russian-born soprano, who has Austrian citizenship, is scheduled to appear for a further three dates this month.
The opera's artistic director, Matthias Schulz, told Berlin public radio that "we have to be careful not to use artists as scapegoats".
Berlin Mayor Kai Wegner, said he was "very critical" of her return to the Berlin stage, regretting than such an internationally successful performer "has not yet clearly and unambiguously distanced herself from the Russian war of aggression and Putin".
The city's senator for culture, Joe Chialo, pointedly attended a photo exhibition on Friday entitled Russian War Crimes, across the road from the opera house on Berlin's Unter den Linden.
He was joined by Ukrainian ambassador Oleksii Makeiev, who said on social media that people should not turn a blind eye to Russian war crimes.
Ms Netrebko, who lives in Austria, was dropped by the Metropolitan Opera in New York after she refused to denounce Mr Putin.
Last March, she made a statement saying she "expressly" condemned the war, adding: "I am not a member of any political party nor am I allied with any leader of Russia. I acknowledge and regret that past actions or statements of mine could have been misinterpreted."
She endorsed Mr Putin as president in 2012 and two years later she was photographed holding a pro-Russian proxy flag, having donated money to an opera house in the occupied Ukrainian city of Donetsk.
However, the singer has said she has met Mr Putin "only a handful of times in my entire life" and insists she has received no financial support from the Russian government.
Last year the Berlin State Opera said Ms Netrebko had agreed that she would not take part in a 2022 opera but its position has since changed.
In a recent announcement explaining its decision to cast Ms Netrebko, the opera stressed the importance of distinguishing between her actions before and after the outbreak of the war.
"Since the outbreak of the war, Anna Netrebko has not accepted any engagements in Russia and her management has confirmed to us that there are still no plans for any appearances in Russia," it said.