Tens of thousands of people have gathered in Moscow for a rally against Vladimir Putin's presidential victory waving flags and banners, and wearing white ribbons that have become the symbol of the movement fighting for free and fair elections.
Organisers say that about 25,000 people attended the march in the Russian capital on Saturday, about a quarter of the size of the last protest before the March 4 which poll gave Putin a six-year third term as president.
Police estimated the crowd at 10,000 and independent witnesses put it at under 20,000.
At the end of the tightly policed rally, leftist leader Sergei Udaltsov attempted to lead an unsanctioned march of around 60 people to a central square, but police roughly detained him and several others.
Even though international vote monitors say the election was skewed in his favour, most opposition leaders have been forced by the margin of victory to acknowledge that Putin was the winner.
Officials results showed the prime minister and former KGB officer won almost 64 per cent of votes and put the runner-up,
Communist Gennady Zyuganov, on less than 18 per cent.
The opposition is struggling to find a way to maintain pressure on Putin and mount a sustained challenge to the man they say has stunted Russia's political and economic development after 12 years rule as president or prime minister.
Udaltsov has called for one million people to march on May 1, a national holiday.
"[The] opposition remains a very disparate group, and bringing them together is proving to be quite a challenge "
- Al Jazeera's Charles Stratford
"Only the street can change the authorities. Only the masses. We have no other option." he said.
"That's why we'll be fighting, going onto the streets - until we overthrow."
But organisers did not agree on a date for the next protest and many said the opposition has to be patient over its demands for a more open political system and greater democracy.
"If this system took 15 or so years to be created, we need a few years - three, four, five - to dismantle it," Yavlinsky said.
Al Jazeera's Charles Stratford, reporting from Moscow, said that part of the problem was the "opposition remains a very disparate group, and bringing them together is proving to be quite a challenge".
"There is a still a question of a leader for the opposition movement. They vow to push on ang they will keep on marching until the inaugaration," he said.
Earlier on Saturday, police were highly visible in Moscow, lurking in buses parked around the city after the last rally on March 5 ended in mass arrests when some protesters refused to leave the venue.
According to Moscow police, about 2,500 members of the security forces were to be on duty at the rally.
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Stratford said the atmosphere at the rally has been calm so far.
"There are tens of military vehicles and police here as well," he said.
"We also saw buses carrying riot police and there are security helicopters hovering overhead.
"Opposition figures have been speaking to the crowds saying the elections have been rigged.
"The response by the crowds was somewhat muted in comparison with the rallies right after Putin's victory on Sunday."
Activists said the rally would focus on violations in the presidential polls, which according to independent monitoring group League of Voters, "discredited the Russian presidency, the electoral system and the whole state".
"The main slogans of the meeting were 'For honest elections', 'For honest authorities' and 'Putin is not our president,'" Udaltsov told the Interfax news agency.
After holding four mass protests over the last three months, and successfully breaking the taboo against opposition rallies in Russia, the movement now faces a huge challenge to decide where to go from here.
The involvement of nationalist leaders and the sometimes inflammatory rhetoric of one of the most charismatic of the opposition leaders - the anti-corruption crusader Alexei Navalny - has also discomforted some liberals.
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"For the first time in months, I am having doubts about whether to go to the next protest," Oleg Orlov, who heads rights group Memorial, wrote on a blog for the Moscow Echo radio.
"Why is it that at every meeting I and my friends have to listen to radical nationalists?"
The protest comes a day after Barack Obama, the US president, telephoned Putin to congratulate him on his election victory. The call came several days after other world leaders hinted at the importance of the US-Russian relationship.
The controversy over elections and the demonstrations has on occasion tested US-Russia ties, with Putin accusing Washington of funding NGOs with the aim of questioning the polls and sparking protests.
Putin, currently prime minister, won 63.6 per cent of the vote in the elections and is now preparing for a May inauguration to take back the Kremlin job he held from 2000 to 2008 from his protege Dmitry Medvedev.
Source: Al Jazeera and agencies