One of Putin's fiercest critics has vanished and the Russian government is not talking

After two weeks without word from Aleksei A. Navalny, Russia’s most prominent opposition figure, his lawyers and allies, fearing the worst, are running a frantic campaign to find him.

Their efforts have included requesting information from dozens of Russian prisons and taking to social media to raise awareness of Mr. Navalny’s disappearance and to call on the Russian government to reveal his whereabouts.

Many Russians living abroad have gone to their country’s diplomatic missions to protest. Some have held up posters saying “Where is Navalny?”

Dmitri S. Peskov, spokesman for President Vladimir V. Putin, told journalists on Friday that the Kremlin had “neither the possibility, nor rights or desire to trace the fate of convicts,” referring to Mr. Navalny.

Here is what we know about Mr. Navalny and his disappearance.

The last time Mr. Navalny’s lawyers heard from him was on Dec. 5. The following day, one of his lawyers waited for seven hours outside the penal colony where Mr. Navalny was being kept but was not allowed to see him, Kira Yarmysh, a spokeswoman for Mr. Navalny, said. Mr. Navalny then failed to appear by video link at a scheduled court hearing the next day, Dec. 7.

In the days after Mr. Navalny’s disappearance, his allies grew more alarmed as letters sent to him went undelivered and the authorities declined to reveal his location to his lawyers. On Dec. 11, officials in the prison colony that had been holding Mr. Navalny — in Melekhovo, a town about 160 miles east of Moscow — told his lawyers that he was no longer listed among its inmates, Ms. Yarmysh said.

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