Prime minister Vladimir Putin has accused the United States of stirring up protests against his 12-year rule and said foreign countries were spending hundreds of millions of dollars to influence Russian elections.

In his first public remarks about daily demonstrations over allegations that Sunday's election was slanted to favour his ruling party, Mr Putin said US secretary of state Hillary Clinton had encouraged Kremlin opponents by criticising the vote.

"She set the tone for some opposition activists, gave them a signal, they heard this signal and started active work," Mr Putin told supporters as he laid out plans for his campaign to return to the presidency in a March election.

Citing the examples of Ukraine's 2004 Orange Revolution and the removal of governments in Kyrgyzstan - also a fellow former Soviet republic - that were accompanied by bloodshed, he said Western nations were spending heavily to foment political change in Russia.

"Pouring foreign money into electoral processes is particularly unacceptable," he said.

"Hundreds of millions are being invested in this work. We need to work out forms of protection of our sovereignty, defence against interference from outside.

"We have to think of ways to tighten accountability for those who carry out the aims of foreign states to influence domestic political processes."

Sorry, this video has expired Protesters chant 'Russia without Putin' and carry banners reading 'You were cheated'

Anti-Western rhetoric

Mr Putin's remarks echoed the tough anti-Western rhetoric he employed in his 2000-2008 presidency to suggest Western nations were funding Kremlin foes to try to weaken Russia and prevent its resurgence after the collapse of the Soviet Union in 1991.

He has turned increasingly to the same tough talk since revealing in September that he planned to swap jobs with president Dmitry Medvedev next year.

Accepting his United Russia party's nomination as a presidential candidate last month, he warned that the West would seek to influence the parliamentary and presidential votes.

"What is there to say? We are a big nuclear power and remain so. This raises certain concerns with our partners. They try to shake us up so that we don't forget who is boss on our planet," Mr Putin said.

The United States and the European Union have expressed concern about the conduct of the Russian election and the treatment of peaceful protesters.

Ms Clinton suggested on Tuesday that the vote was not free or fair.

Falling approval

Voters bruised Mr Putin in Sunday's election by sharply reducing his party's majority in the State Duma lower house, undermining his mandate as he prepares to return to the Kremlin in the March 4 presidential vote.

Mr Putin remains Russia's most popular politician three months before the election for a six year-term as president. He could then run again, potentially serving until 2024.

But polls show his approval rating has fallen from previous heights, and the sharp decline in support for his ruling party was a sign of frustration with the political system he has put in place, in which many Russians feel they have no influence.

About 5,000 people turned out on Monday night for the largest opposition protest in Moscow in years, demanding fair elections and chanting "Russia without Putin!".

Police have detained more than 1,000 people in Moscow and St Petersburg, many of them briefly, in a crackdown since Sunday, but opposition groups are planning new protests on Saturday, including one close to the Kremlin in the capital.

Mr Putin depicted some of the protesters as self-interested politicians who were not acting in the interests of the country.

"We are all adults here and we understand that some - I am not saying all - but some of the organisers act in accordance with a well-known scenario and in their own mercenary political interests," he said.

Reuters