The rapper, Oxxxymiron, said proceeds from his show would go to help Ukrainian refugees. Russians at the concert denounced the war but said they felt helpless to stop it.

“I hate feeling so powerless,” Oxxxymiron, one of Russia’s most popular rappers, said at a benefit concert for Ukrainian refugees at an Istanbul club on Tuesday.Credit...Sergey Ponomarev for The New York Times

— Only a month ago it would have been an innocuous scene in Moscow: Oxxxymiron, one of Russia’s most popular rappers, performing his latest tracks onstage with a banner behind him reading: “Russians against war.”

But after President Vladimir V. Putin decided to invade Ukraine, what had been typical for the rapper, known for his political sloganeering, quickly became impossible.

On Tuesday, instead of playing one of a string of six long-anticipated, sold-out arena shows in Moscow and St. Petersburg, Oxxxymiron gave an antiwar concert in a packed club in Istanbul, while streaming the performance on YouTube and other platforms in the hope that people in Russia would watch and donate. He promised that all proceeds, including ticket sales, would go to help the more than three million Ukrainian refugees who have fled Russian aggression.

A crowd of Russians, many of whom had left their own country over the past three weeks, fearing Mr. Putin’s tightening oppression, filled a club in Istanbul’s trendy Kadıköy district, chanting “No to war!” and “Glory to Ukraine!” — slogans that could now get them jailed at home.

“Millions in Russia are against this war,” said Oxxxymiron, also known as Miron Fyodorov.

“I hate feeling so powerless, but I understand well that what we are doing today is the absolute minimum,” he said during the concert. “This is important not only to Ukraine but to Russia, too, which we can lose.”

Thanks to the internet, rap has become a dominant genre in Russian pop culture over the past few years, with new stars defying the government’s preferred aesthetics and values. At one point the Kremlin, worried that it might lose the loyalty of young Russians, put pressure on some of the most outspoken rap artists and shut down concerts.

ImageOutside the club before the show. Tens of thousands of Russians have moved to Istanbul since the war in Ukraine began.

Oxxxymiron has been a pioneer of the movement and a symbol of the post-Soviet generation of globalized Russians. After growing up in Russia and Germany, and getting a degree at Oxford, he returned to his native St. Petersburg and quickly became an ambassador of Russian rap on the international stage.

Oxxxymiron may now be seen as one of Russian rap’s old guard, but his sentiments about the war are shared by many Russian artists across genres. Many of them either started their careers in Ukraine before moving to Russia or toured actively in Ukraine, building a fan base there.

After Valery Meladze, a pop singer who had regularly appeared on state-run channels, called for the war to end as soon as possible, he was quickly removed from some music channels in Russia, along with other pro-Ukrainian and Ukrainian artists.

The rapper Face said that he had fled Russia and that he “practically” was no longer a Russian artist or citizen.