Tens of thousands of people have demonstrated in support of Prime Minister Vladimir Putin in cities across Russia, in a show of force two weeks before a presidential election that is expected to return him to the Kremlin.

The rallies began along Russia's eastern areas, notably in Vladivostok, on Saturday, and culminated in a late-night demonstration on wheels in Moscow, where motorists took to the streets with slogans such as "Putin rules" displayed on their cars.

"One wish unites us: we want to be sure of tomorrow," said a declaration read out at the rally in St. Petersburg, which like many others was organised by trade unions that have close government ties.

The declaration urged Russians to vote on March 4 and to "defend the right to the stable future".

In central Moscow, about 10 people who staged a street protest against Putin were detained, local media reported.

The rallies in support of Putin were aimed at showing that the prime minister still retains the majority of Russians' support, despite the biggest opposition protests of his 12-year rule as president and now prime minster.

Opponents allege that state workers have been pressured to attend the pro-Putin demonstrations with a combination of threats and pyaments, and that the police have been exaggerating the size of crowds at such gatherings, while underestimating the size of opposition protests.

Tens of thousands of people have turned out for opposition protests in recent months, venting anger over suspected fraud in December's parliamentary elections.

On February 4, when opponents held their most recent large-scale protests in Moscow, supporters of Putin staged a rally that may have been even bigger. He has criticised the opposition protests as being organised by foreign governments and the protesters as being bent on revolution.

Rally for stability

At Saturday's rallies, demonstrators said they wanted stability, which Putin says he brought to Russia after the economic troubles ushered in by the 1991 collapse of the Soviet Union.

Authorities said crowds of thousands gathered in many cities, with as many as 60,000 in St. Petersburg, Russia's second  city and the hometown of Putin.

In Oryol, a city south of Moscow, demonstrators chanted "Russia, Putin, Victory!" and vowed "to prevent new upheaval".

"We have come to this rally today to say that we do have something to defend. We want to say as loudly as possible that we support Vladimir Vladimirovich Putin," youth movement leader Ivan Arkatov told the crowd, according to the Itar-Tass news agency.

"We stand for the unity of the country and for stability," Itar-Tass quoted a student activist in the Volga River city of Nizhny Novgorod as saying. "We are the people of Russia and we will decide Russia's fate."

The pro-Putin car rally in Moscow late on Saturday followed a similar demonstration against Putin, and in favour of fair elections, that was organised by opposition activists on January 29. They plan another car protest on Sunday.