Demonstrators trying to hold a second day of protests against vote fraud in Russia's parliamentary elections have clashed with police in Moscow.
Hundreds of officers blocked off Triumphal Square, then began chasing about 100 demonstrators, seizing some and throwing them into police vehicles.
Prime Minister Vladimir Putin's United Russia party saw a significant drop in support in Sunday's election but it will still have a majority in parliament. Opponents say even that watered-down victory was due to massive vote fraud.
In neighbouring Lithuania, US Secretary of State Hillary Clinton again criticised the Russian election and urged that widespread reports of voting fraud be investigated.
Some Moscow demonstrators shouted "Putin is a crook and a thief!" referring both to the alleged election fraud and to widespread complaints that United Russia is one of the prime reasons for Russia's endemic corruption.
Among the detained was Boris Nemtsov, a leader of the liberal opposition, along with prominent radical Eduard Limonov and Oleg Orlov, head of the renowned human rights group Memorial.
Hundreds of young men with emblems of United Russia's youth wing, the Young Guards, also gathered on the outskirts of the square and tauntingly chanted "Putin victory!"
Large crowds also gathered on a square in St Petersburg, outnumbering police.
United Russia won slightly less than 50% of Sunday's vote, according to nearly complete preliminary results. Although that gives the party an absolute majority in the State Duma, the lower house of parliament, it is a significant drop from the 2007 election when the party got a two-thirds majority, enough to change the constitution unchallenged.
Yet Sunday's election results reflected public fatigue with Putin's authoritarian streak and with official corruption in Russia, signalling that his return to the presidency in next March's election may not be as trouble-free as he expected.
Mr Putin, meanwhile, called his party's reduced number of seats in Sunday's parliamentary election an "inevitable" result of voters always being dissatisfied with the party in power. He also dismissed allegations of corruption among his United Russia party members, calling it a "cliche" that the party had to fight.
Russia's beleaguered opposition has been energised by the vote. Late Monday, thousands marched in Moscow chanting "Russia without Putin!"
On Tuesday evening, hundreds of police cordoned off Triumphal Square, adjacent to the capital's main boulevard, after reports that anti-Putin demonstrators would try to gather there. Hundreds of young men, some wearing emblems of the Young Guards, United Russia's youth wing, also were seen at the square.
Police also cordoned off a monument to the 1905 Revolution, which also has been the site of demonstrations.
Police detained about 300 protesters in Moscow on Monday and 120 participants in a similar rally in S. Petersburg.
Security forces already had been beefed up in the capital ahead of the election. Moscow police said 51,500 Interior Ministry forces were involved and it was all part of increased security for the election period.
Mr Putin's comments appeared aimed at saving face and discouraging the opposition from seeing United Russia as vulnerable.
"Yes, there were losses, but they were inevitable," he said. "They are inevitable for any political force, particularly for the one which has been carrying the burden of responsibility for the situation in the country."
He also addressed the popular characterisation of United Russia as "the party of crooks and thieves," saying corruption was a widespread problem not limited to a single party.
"They say that the ruling party is associated with theft, with corruption, but it's a cliche related not to a certain political force, it's a cliche related to power," he said.
"What's important, however, is how the ruling government is fighting these negative things."
Mrs Clinton criticised the vote for a second straight day, saying that "Russian voters deserve a full investigation of electoral fraud and manipulation."