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Kremlin officials and Russia's opposition on Tuesday gathered to pay tribute to Russia's most prominent human rights activist, Lyudmila Alexeyeva, who died at age 91.

Alexeyeva, a staunch and uncompromising rights advocate, made a name for herself in the 1960s and '70s protesting the treatment of Soviet political prisoners. She returned to Russia in 1993 after spending more than two decades in exile, and continued to be an energetic champion for human rights.

Alexeyeva has been lauded as a bridge-builder. A scathing critic of the Kremlin's ongoing crackdown on rights and activism, she nevertheless sat on the government's council for human rights and tried to work with officials to help people in need.

Friends, family as well as political figures including President Vladimir Putin and opposition leader Alexei Navalny on Tuesday came to pay their respects at a community center in central Moscow where the wake was held.

Putin sat down with Alexeyeva's family for a couple of minutes before leaving. In his message of condolences he hailed her as a "courageous and strong person who has always been true to her beliefs." Later that day, Putin called a moment of silence in Alexeyeva's memory before chairing the presidential council for human rights.

In a chilling symbol of the state of the Russian civil society, one of Alexeyeva's associates, Lev Ponomaryov, was sentenced last week to 16 days in prison over a Facebook post. He petitioned to be released to say his goodbyes to Alexeyeva; a court rejected his motion.

Former Soviet leader Mikhail Gorbachev in a statement on Tuesday hailed her as a "believer in Russia's democratic future" while Alexei Navalny, speaking to the television channel Dozhd, said Russia's human rights movement "has lost its mother."

Alexeyeva's son Mikhail, who teaches economics in the United States, thanked the gathering for messages of support and said that Alexeyeva was not only a person who helped a lot of people but also "was the best mom anyone could imagine."

Alexeyeva will be cremated at a cemetery in Moscow and her ashes will be taken to the U.S., where her husband is buried.