Moscow: Facing rare street demonstrations against his rule, Prime Minister Vladimir Putin on Thursday accused the US of instigating post-election protests in Russia that are posing a challenge to his authority.

In a throw-back to the Cold War era, Putin charged US Secretary of State Hillary Clinton and the State Department with sending signals to the opposition to protest the fairness of the just-concluded polls to the State Duma, lower house of Parliament.

Clinton "has described the polls unfair, even before seeing the report of OSCE (Organisation for Security and Cooperation in Europe) poll monitors," Putin said in his first comments on the wave of demonstrations taking place in the Russian capital.

She has "set the tone for opposition activists," he charged, saying that the US Secretary of State was giving signals to the protesters with the backing of the State Department.

In a televised address to his supporters, Putin accused Washington of funding Russian NGOs to the tune of "millions of dollars" to question the validity of the elections.

His hard-hitting comments come after Clinton complained that the polls were neither free nor fair, a concern also voiced by former Soviet President Mikhail Gorbachev.

Putin's ruling United Russia party suffered a setback, losing large numbers of seats, although managing to retain simple majority in State Duma.

Putin said the US was uncomfortable with Russia remaining a nuclear superpower and was trying to make its government pliant by making inroads into its domestic politics.

"We cannot allow them (US) to influence our domestic political processes and we are obliged to defend our sovereignty," Putin said, adding steps should be taken "against those who act on foreign orders."

Amid preparations by the non-Parliamentary opposition for more protest rallies over the weekend, he said that "street democracy" will continue as long as protesters remain within the law.

"As far as acts of street democracy go...if people act within the law, they should be given the right to express their opinion and we should not restrict anybody's civil rights," Putin said.

"If anyone breaks the law, law enforcement bodies should demand they observe the law, using all legitimate methods."

He said the overwhelming majority of Russians was against repetition of Kyrgyz or Ukrainian scenarios in Russia which, he alleged, were financed by the US under the project of "coloured revolutions".

"Majority of the citizens are against chaos," he said.

In the past four days of protests, over 1,000 people have been detained in Moscow and St Petersburg alone and the central parts of Moscow are full of interior troops and riot police popularly called 'cosmonauts' because of their typical helmets.

Over 25,000 people have so far said on social network sites like Facebook and home-grown 'VKontakte' that they will attend a sanctioned protest planned for downtown Moscow's Revolution Square on Saturday.

The authorities have allowed the radical opposition group 'Solidarity' to hold a demonstration of 300 people and cautioned that the organisers would face prosecution if more people turned up.

The square was closed for what officials say is sewage repair work yesterday. An ice theatre is also due to open on the square on Saturday.

(Agencies)