Several hundred demonstrators rallied in Moscow on Tuesday to press for the release of opposition activists on the same day that Russia commemorated the victims of Soviet-era repression.

Protesters demanded that authorities free more than a dozen people who are in jail facing accusations over their role in a May protest that turned violent, among other charges. The opposition calls them "political prisoners."

President Vladimir Putin has launched a multi-pronged crackdown on dissent since being inaugurated for a third term in May. He has signed off on several repressive laws and allowed numerous arrests and searches of opposition activists.

One of the jailed activists, Leonid Razvozzhayev, said he had been abducted from Ukraine while seeking a political asylum and smuggled back into Russia where he was tortured into confessing. Russian authorities say he turned himself in.

Participants in the rally, which ended peacefully, demanded punishment for those involved in the abduction and torture of Razvozzhayev.

Leftist leader Sergei Udaltsov, who himself is facing charges of plotting riots which he has rejected as politically motivated, called on opposition supporters to keep pressing for the jailed activists' release or face a "long totalitarian winter."

The rally came on the day when Russia paid tribute to the victims of Soviet-era repression. Mourners attended a church service Tuesday at a former firing range at Moscow's district of Butovo, where some 20,000 priests, artists and other "enemies of the people" were executed at the height of Soviet dictator Josef Stalin's purges.

Millions of Soviet people were sent into prison camps and either died there or were executed in mass purges that continued until Stalin's death in 1953.

Prime Minister Dmitry Medvedev marked the day by issuing a harsh criticism of Stalin, which contrasted with a more cautious stance taken by Putin, who has restored Soviet-era symbols and tried to soften public perceptions of Stalin in the past.

Medvedev told members of the Kremlin's United Russia party that Stalin and his entourage committed a grave crime by "waging a war against their own people."