Russia's opposition groups have vowed to go ahead with Saturday's protest march against President Vladimir Putin in Moscow, despite an official ban.
Opponents of President Vladimir Putin have staged a protest against what they see as the Russian leadership's increasing authoritarianism.
The rally is being organised by former chess world champion Garry Kasparov, who has said its participants would try to avoid any possible provocations.
Organisers, including former chess champion Garry Kasparov, had hoped up to 5,000 people would attend. But turnout was about 2,000.
The march is against what protesters describe as rampant corruption and a Kremlin crackdown on democracy.
Some witnesses said their numbers were dwarfed by the police and security service presence in central Moscow.
A pro-Kremlin youth group plans to hold its own demonstration on Sunday.
A police helicopter flew overhead, threatening to drown out chants.
'Uniting opposition'
The demonstration comes 15 months before the next presidential election.
Mr Kasparov will be leading the rally, described as "the march of those who disagree".
Although Mr Putin is not eligible to stand, analysts believe his popularity is such that whoever he backs is assured of an easy victory.
The organisers accuse Mr Putin of silencing dissent
The 2,000 or so protesters were kept confined behind barriers and surrounded by helmeted riot police, says the BBC's James Rodgers in Moscow.
He has said that the authorities are violating his constitutional rights by banning the march.
Today we finally came together and called for our collaborators and supporters that we start our political process to change this particular power Mikhail Kasyanov Former PM
Its organisers say they have been ordered by the Moscow city authorities to remain in one square.
Some reports suggested thousands of riot police and soldiers were on the streets for the protest.
And activists in a number of Russia's regions, who planned to travel to the capital to participate, claim they have been ordered to report to police stations instead.
The anti-Putin lobby ranged from radical youth groups to communists nostalgic for the Soviet Union to free marketeers.
"We took additional steps to maintain the format of the action and avoid outright clashes, which we realise could end badly," Mr Kasparov told a news conference in Moscow.
Former Russian Prime Minister Mikhail Kasyanov - now a Kremlin opponent - insisted this was a significant and important day.
He said the march would unite "opposition forces of different political persuasions".
"Today we finally came together and called for our collaborators and supporters that we start our political process to change this particular power. Fight together with us, politically, and get prepared for elections.
The organisers are expecting about 4,000 people to join the march.
Mr Kasparov left professional chess to devote his attention to opposition politics and now runs an organisation called the United Civil Front.
A pro-Kremlin youth group plans to hold its own demonstration a day later.
The Russian opposition has long been wracked by internal divisions, the BBC regional analyst Stephen Eke says.
It says it plans to attract more than 100,000 participants, but no restrictions have been imposed on it.
But he adds that with parliamentary elections due next year, and presidential elections due early in 2008, they have begun to co-ordinate their efforts.
Offices raided
Mr Kasparov left professional chess to devote his attention to opposition politics, the BBC's Russian affairs analyst Steven Eke says.
Mr Kasparov now runs an organisation called the United Civil Front - an umbrella group which brings together a motley array of liberal free marketeers, nationalists and radical youth movements.
The Russian opposition has long been wracked by internal divisions, our analyst says.
But he says that with parliamentary elections due next year, and presidential elections due early in 2008, they have begun to coordinate their efforts.
They are angered, especially, by recent changes to Russian electoral law, which, they say, are designed to push the smaller, opposition parties out of the race.
Already, Russia's parliament is dominated by pro-Kremlin parties that generally rubber-stamp laws proposed by the government, our analyst says.
However, the authorities have already made clear that they view Mr Kasparov's activities as potentially subversive.
Earlier this week, more than a dozen officers from the FSB, Russia's domestic security service, raided his office to remove documents and equipment.
