Saint Petersburg (AFP) - Russian police violently broke up a rally in Saint Petersburg as thousands took to the streets across Russia Saturday on President Vladimir Putin's 65th birthday, urging him to quit power.

Heeding the call of jailed opposition leader Alexei Navalny to demand competitive elections, around 3,000 people rallied in Russia's second city and Putin's hometown while more than a thousand demonstrated in the centre of Moscow, AFP reporters said. Protests were held in around 80 cities throughout the country.

More than 270 people were detained nationwide, more than 60 of them in Saint Petersburg, according to OVD-Info, a group that monitors politically motivated arrests.

But while police in rainy Moscow showed restraint, allowing the crowd of mostly young protesters to march in the city centre in an apparent effort to avoid clashes on Putin's birthday, the rally in Saint Petersburg ended in violence.

Activists chanted "Shame" as helmeted police threw some protesters into police vans, injuring several demonstrators and forcing some to run for cover, an AFP reporter and witnesses said.

Igor Klimov, a 20-year-old protester, said he was not happy with Putin.

"He has been in power for as long as I can remember and there's corruption everywhere," he told AFP.

- Right to 'peaceful protest' -

Photographs from the scene showed a woman clutching her bleeding head after being detained by officers at the unauthorised protest.

Amnesty International called on Russian authorities to immediately release the protesters and investigate instances of violence.

"The Kremlin’s intent is clear – to choke the life out of the protest movement," said Denis Krivosheev, Amnesty's deputy director for Europe and Central Asia.

"Peaceful protest is a right, and many people in Russia want to exercise that right. The Russian authorities must immediately begin to respect and protect the rights of these protesters, pure and simple," he said.

The protests -- called by Navalny after he was sent to jail for 20 days this week -- were markedly smaller than the rallies he mustered in March and June when tens of thousands took to the streets against corruption.

Story continues

The number of people detained across Russia on Saturday is lower than the arrests during the rallies called by Navalny in March and June. Police detained more than 1,000 people in Moscow alone during the March demonstration.

In Moscow on Saturday, the crowd chanted "Happy birthday" and "Russia without Putin" and many held copies of the constitution and waved flags amid honks of support from passing cars.

Hundreds of police officers, some in riot gear and with dogs, were deployed to prevent people from going to Red Square.

Navalny, a charismatic anti-corruption campaigner who aims to run in a presidential election next March, was arrested late last month as he was planning to travel to a rally in a provincial city.

A court on Monday sentenced him to 20 days in jail on charges of repeatedly violating a law on organising public meetings.

Officials say he is not eligible to run for president because he is serving a suspended sentence for fraud.

- 'Important to have choice' -

Svetlana Kiseleva, a 20-year-old student in Moscow, said she did not support Navalny but had joined the rally to demand political competition.

"It's important to have a choice, to have an opposition," she told AFP. "I still think he would be better than Putin anyway."

Putin, who has ruled since 1999, turned 65 -- the retirement age for Russian officials -- and many protesters urged him to step down.

He said this week he has not yet decided whether to seek another six-year term. But he is widely expected to run in -- and win -- the March election.

- 'Gulag awaiting us' -

Navalny's campaign team had released a series of video addresses of prominent figures calling on Russians to take to the streets.

"Gulag is awaiting us without political competition," entrepreneur Evgeny Chichvarkin, who lives in self-imposed exile in Britain, said in the video.

Navalny, the Yale-educated lawyer with a street-smart image and a penchant for catchy slogans, compared life under Putin's regime to a forced diet of "turnip."

"If we do nothing, they will be feeding us this damn turnip for the rest of our lives. And our children too," he said in an address dictated from his cell this week.

The Kremlin said Putin received on his birthday "numerous congratulatory messages and telegrams" including from 11 heads of state and later met with members of the Russian security council to discuss Syria.