Opposition leaders on Sunday laid flowers at the memorial to the victims of the August 1991 coup attempt against Soviet President Mikhail Gorbachev.
Alexei Navalny, Boris Nemtsov, Vladimir Ryzhkov and Mikhail Kasyanov came to commemorate the event that contributed to the end of the Soviet Union.
"It's a good example of a peaceful revolution," Nemtsov, who at the time was a parliamentary deputy and vehement supporter of the president, said during Sunday's 500-person rally near the White House.
The memorial to the "Defenders of Democracy" commemorates three young men — Vladimir Usov, Ilya Krichevsky and Dmitry Komar — who died on Aug. 21, 1991, while trying to stop tanks headed toward the White House.
At Sunday's rally, a girl wearing a balaclava in support of Pussy Riot was detained by police. The arresting officers cited a newly passed law that prohibits the wearing of masks at public gatherings.
Opposition figures recalled the three-day struggle 21 years ago with reproach.
"Those who came to power because of the events of 1991 are worse than those who came before," left-leaning Just Russia Deputy Ilya Ponomaryov told RBC on Sunday.
He added, "I believe that those who took to the streets didn't want such a fate for their country."
According to a survey last week by the independent Levada Center, more than 40 percent of Russians see the August 1991 coup attempt as "tragic" for the country.
Thirty-seven percent called it a "power struggle." Only 10 percent said it was a victory for a "democratic revolution."
The August 1991 attempt inspired thousands of Muscovites to storm the garrison around the White House in support of the then-president of the Russian Soviet Republic, Boris Yeltsin, who was in the building at the time.
Yeltsin went on to become the first president of the newly formed Russian Federation four months later.
"I was at my dacha with the children at the time, but my husband was near the White House, and he came back when the victory was achieved," Tatyana Neshumova, in her mid-40s, said after laying flowers at the memorial plaque.
But the unity among the August 1991 victors was short-lived. Two of Yeltsin's staunchest allies, Vice President Alexander Rutskoi and State Duma Speaker Ruslan Khasbulatov, turned against him in 1993.
During the constitutional crisis of 1993, Yeltsin sent tanks to fire on the White House, which by then had turned into a bastion of political forces, both left and right, who opposed his reforms.
"This is unavoidable in any revolution. First you have a common goal to cast away a regime, and then you turn to different sides," said Vladimir, 63, a retired engineer who came to remember the victims of August 1991.