A protester carrying a sign criticizing the policies of President Vladimir V. Putin of Russia climbed over the orchestra pit and onto the stage at the Metropolitan Opera on Thursday night as the diva Anna Netrebko took her curtain call after performing the title role in Tchaikovsky’s “Iolanta.”

The protester unfurled the sign, which appeared to be decorated with the Ukrainian flag, just as Ms. Netrebko was being showered with bravas and a bouquet of flowers. After unfolding the sign, the man showed it to the audience, turned to show it to the startled performers and was then escorted off the stage. Met officials said that he had been arrested. His name was not immediately available.

Ms. Netrebko and the conductor for the performance, Valery Gergiev, have both been vocal supporters of Mr. Putin, and have faced protests in the West over anti-gay legislation in Russia as well as Russia’s actions in Crimea and eastern Ukraine. Last month Ms. Netrebko donated a million rubles — roughly $18,500 — to the opera house in Donetsk, a war-torn city in Ukraine, giving the check to Oleg Tsarov, a separatist politician, at a news conference.