Thousands of mourners gathered in Moscow for the funeral of Russian opposition leader Alexey Navalny despite a heavy police presence and the threat of detention.

Mourners clapped and chanted Navalny’s name as his coffin arrived at the church where his funeral took place. Others shouted “Putin is a killer” or “no to war.”

Navalny, Russian President Vladimir Putin’s most formidable opponent, died aged 47 in an Arctic prison on February 16, sparking condemnation from world leaders and accusations from his aides that he had been murdered. The Kremlin has denied any involvement in his death.

Navalny’s team encountered difficulty in retrieving his body from Russian authorities and hiring a venue for his funeral, which was held Friday afternoon at the Church of the Icon of the Mother of God in Moscow’s Maryino district, where the Kremlin critic lived.