Between 300 and 400 activists took part in new opposition organization Solidarity's first major event on Sunday, said Lev Ponomaryov, a leading human rights advocate who participated in the conference.

A list of the country's leading opposition politicians, including United Civil Front leader Garry Kasparov, former Deputy Prime Minister and SPS co-leader Boris Nemtsov, Young Yabloko leader Ilya Yashin, the leader of the party's St. Petersburg chapter Maxim Reznik and former deputy energy minister Vladimir Milov, were on hand at the Izmailovo Hotel in the east of the city, although repeated calls to the hotel to verify the number of attendees went unanswered.

"The authorities have destroyed the democratic process in Russia," Ponamaryov said. "The most important goal of the new organization is to dismantle the regime."

Despite the new organization's name, the absence of People's Democratic Union leader and former Prime Minister Mikhail Kasyanov, Yabloko leader and Moscow Duma Deputy Sergei Mitrokhin and Eduard Limonov, leader of the now-defunct National Bolshevik Party, did not attend.

"We will not work with them," Mitrokhin said Sunday. "This is a parody of the Polish Solidarity movement."

"I have great respect for Solidarity because it worked with the people. The people who are gathering together in Russia under this new name only know how to handle their own PR and nothing more," Mitrokhin said.

The opposition leader questioned the need for a new organization to oppose extension of presidential terms from four years to six, proposed by President Dmitry Medvedev at the beginning of the month and passed on third reading by the State Duma on Friday.

"Why organize a new party to oppose the six-year term when we are already organized against it?" Mitrokhin said.

Neither Kasparov nor Nemtsov, the main organizers of the congress, answered repeated calls to their phones on Sunday.

Concerns ahead of the event that the authorities would try to interfere proved to be unfounded, as there was no significant law enforcement presence at the hotel complex.

"Everything was calm," Yashin said.

Solidarity plans to hold a founding congress on Dec. 13, a date Nemtsov described as "symbolic" because Russia marks Constitution Day on Dec. 12.