MOSCOW — Russian news reports say a prominent opposition figure who was recently released after serving more than four years in prison has been detained again ahead of an unsanctioned rally in Moscow.

Sergei Udaltsov, leader of the Left Front, was among about 30 people detained in connection with the demonstration, the reports said Saturday.

The Interfax news agency cited Udaltsov’s attorney, Violetta Volkova, as saying he is to appear in court Monday on a charge of disturbing public order. The charges carry a potential jail time of 15 days.

Udaltsov was released from prison in August after serving 4½ years on charges related to his role in staging a May 2012 protest rally on the day before Vladimir Putin’s return to the presidency.