The Russian opposition leader has been jailed after mass rallies against President Vladimir Putin were held across the country, and if the fates of his predecessors are any guide he has reasons to be very worried.

Alexei Navalny was found guilty of breaking regulations on the organisation of demonstrations, his spokeswoman Kira Yarmish said. Mr Navalny was jailed for 30 days by a Moscow court on Monday.

Protests against Mr Putin were held in more than 100 cities and towns across the country on Monday, the patriotic Russia Day holiday. Mr Navalny was arrested at his home before he could join them.

Anti-corruption watchdog OVD-Info said more than 700 people were taken into custody at the Moscow protest and more than 500 detained in St Petersburg. State media put the number detained in Moscow at 200.

Alexei Navalny leaves a detention centre in Moscow in March 2015 after spending 15 days in custody for handing out leaflets in the subway. Photo: Getty

Police formed several cordons at the Moscow rally to disperse the crowd and detained protesters who resisted.

Mr Navalny is not the first Kremlin critic to have been prosecuted or silenced, with many of Mr Putin’s political opponents dying in mysterious circumstances.

Denis Voronenkov shot dead – 2017

Former Russian MP Denis Voronenkov was shot dead on a Kiev street in March this year after fleeing to Ukraine.

Ukraine President Petro Poroshenko accused Russian authorities of “state terrorism” over the assassination, the Guardian reported at the time. Mr Putin called the suggestion he was involved “absurd”.

Denis Voronenkov, former member of the communist faction in Russia’s State Duma, speaks during an election campaign in May 2016. Photo: Getty

A gunfight broke out between Mr Voronenkov’s bodyguard and the assassin, who later died.

Mr Voronenkov, 45, was a former member of Russia’s Communist party. He fled the country in 2016 and became a vocal critic of Mr Putin.

Boris Nemtsov shot dead – 2015

Boris Nemtsov attends a rally in Moscow in October 2013. Photo: Getty

Former deputy prime minister Boris Nemtsov was shot four times in the back while walking across a bridge near the Kremlin in February, 2015.

Mr Nemtsov, 55, published reports critical of Mr Putin and accusing him of corruption, the Washington Post reported.

At the time of his death, Mr Nemtsov claimed to have proof Russia was involved with rebels in eastern Ukraine. The Kremlin denied the allegation.

Hours before his death, Mr Nemtsov was promoting a protest against the war in Ukraine. Mr Putin took “personal control” of the murder investigation but it remains unsolved.

Alexander Litvinenko drank poisoned tea – 2006

Alexander Litvinenko is pictured in a London hospital in November, 2006, before dying as the result of a radioactive polonium-210 poisoning. Photo: Getty

Alexander Litvinenko, a former KGB agent, died three weeks after drinking a cup of tea poisoned with polonium-210 after fleeing to England, according to BBC.

A British inquiry found his assassination had “probably been approved” by Mr Putin and was carried out by two Russian agents. Russia refused to extradite them to face trial in Britain, claiming it was against the constitution.

Sergei Yushenkov shot dead – 2003

Sergei Yushenkov is pictured in March 2001. Photo: Getty

Sergei Yushenkov, co-chairman of the Liberal Russia party, was gunned down outside his apartment block in Moscow in April 2003, BBC reported.

He was shot dead just hours after the party had been registered to run at the election.

Mr Yushenkov had been attempting to prove the Kremlin was behind one of the 1999 apartment bombings.

His death came less than a year after the assassination of fellow Liberal Russia member Vladimir Golovlev. Mr Golovlev was being investigated for fraud and some claim his death was tied to the allegations, while others believe it was politically motivated, according to BBC.

Boris Berezovsky found hanging – 2013

Russian businessman Boris Berezovsky stands in front of the Russian embassy in London in May, 2004. Photo: Getty

The Liberal Russia party was financially backed by tycoon Boris Berezovsky. Mr Berezovsky was found hanged in his ex-wife’s bathroom in 2013 after fleeing to the UK and criticising Mr Putin, according to the Guardian.

Mr Berezovsky accused the Kremlin of planning the poisoning of Mr Litvinenko.

Mr Berezovsky’s death was believed to be a suicide but a coroner would not determine the cause of death.

Journalists, humans rights lawyers and political activists have also been jailed or died in mysterious circumstances.