The organizers of the rally include the Moscow Helsinki Group, the Memorial rights center, and the Yabloko and Union of Rightist Forces political parties.
Russian President Vladimir Putin told a cabinet meeting today in Moscow that law-enforcement authorities should do all they can to help in the identification of such victims.
"I ask each government member not to forget about it and to provide assistance in [the search for information and legal rehabilitation] and do everything to make sure that not a single person, not a single victim, remains unknown or unidentified, so that society always remembers and knows about it, so that nobody has the slightest desire ever again to repeat those elements of the past today or tomorrow," he said.
The Day of Soviet Political Prisoners was first commemorated by rights activists in 1974. It has been publicly celebrated since the 1991 collapse of the Soviet Union.
Activists say the date has taken on new meaning in Putin's Russia. Activists accuse Putin of increasing his grip on power and cutting freedoms.
Demonstrators speak with local politicians in Butovo about the destruction of a local forest in July 2006 (RFE/RL)
IS RUSSIAN DEMOCRACY MANAGING? Russian President Vladimir Putin has said Western powers seek to pressure Russia under the pretext of concern over its democratic development. He has said Russia is ready to listen to "well-intentioned criticism," but will not allow anyone to interfere in its internal affairs. The Kremlin has been criticized for stifling political oppostion, increasing central control over the media, and cracking down on the work on nongovernmental organizations.