Garry Kasparov, considered by West as one of the most celebrated foes of President Vladimir Putin, was released from Moscow jail Thursday after serving his five-day sentence for leading a protest march.
The authorities' goal in jailing him "was to send a message," Kasparov said after stepping out of the police car that delivered him to his Moscow home. He predicted he would be arrested again on more serious charges.
"The Putin regime is entering a new phase of confronting its own people," he said.
Riot police arrested Kasparov on Saturday after a demonstration that drew thousands of opposition protesters and ended in clashes and dozens of arrests. In a trial that evening, Kasparov was convicted of leading an illegal march that followed the rally, chanting anti-Putin slogans and resisting arrest.
The protesters charged that authorities were preventing parties challenging the Kremlin-backed United Russia party from freely contesting the Dec. 2 parliamentary elections.
Kasparov's Other Russia coalition, which includes radicals, democrats and Soviet-era dissidents, has drawn wide media coverage but generated little public support. Its ranks expanded in the run-up to the parliamentary vote, though, as mainstream political parties began to complain they faced harassment in the campaign.