MOSCOW (AP) — Thousands of Russians are marching in the streets of Moscow to mark two years since opposition leader Boris Nemtsov was gunned down outside the Kremlin.

Nemtsov was a fierce critic of Russian President Vladimir Putin. His Feb. 27, 2015 death, in what appeared to be a contract killing, sparked an outpouring of anger and fear from Russia's beleaguered opposition movement.

The protest Sunday in Moscow is expected to be the largest opposition gathering since a similar memorial march last year.

Participants carried Russian flags and placards with quotes from Nemtsov including "Russia will be free," ''If there's Putin, there's no Russia," and "Our only chance left is the street."

Similar demonstrations to honor Nemtsov are to take place in cities across Russia, including St. Petersburg and Nemtsov's hometown of Nizhny Novgorod.