Thousands of Russians marched through Moscow shouting slogans such as “Russia will be free!” and “Putin is war!” to mark two years since opposition leader Boris Nemtsov was gunned down outside the Kremlin.

Mr Nemtsov, formerly Russia’s deputy prime minister, was a fierce critic of President Vladimir Putin. His death on 27 February 2015, in what appeared to be a contract killing, sparked an outpouring of anger and fear from Russia’s beleaguered opposition movement.

The protest in Moscow was the largest opposition gathering since a similar memorial march for Mr Nemtsov last year.

Moscow police said 5,000 people attended the event, however organisers said the figure was more likely to be in the tens of thousands.

Green paint was thrown at former Russian prime minister and Liberal opposition leader Mikhail Kasyanov during the second anniversary of Boris Nemtsov's murder in Moscow (EPA ) (EPA)

“It’s very important that after two years people continue to come out and show their solidarity with the ideas for which Boris Nemtsov fought for and gave his life,” said opposition activist Ilya Yashin, who was Nemtsov’s friend and colleague, Interfax news agency reported.

Participants carried Russian flags, banners of opposition political parties and placards with quotes from Mr Nemtsov including “If there’s Putin, there’s no Russia,” and “Our only chance left is the street”.

Many carried cardboard Russian flags with bullet holes in them.

The event largely occurred without incident, but police made several arrests and opposition leader Mikhail Kasyanov was attacked during the march by an unknown assailant who threw green dye in his face.

“This is the hysteria of the government. They do not know what to do. The government is afraid,” Gennady Gudkov, a former deputy of Russia’s lower house of parliament and an opposition activist, said of the attack on Mr Kasyanov.

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After the march, thousands of people went to lay flowers on the site on the central Moscow bridge where Mr Nemtsov was killed by an attacker who shot him several times in the back as he was walking home with his girlfriend.

Similar demonstrations to honour Mr Nemtsov took place in other Russian cities, including St Petersburg and Mr Nemtsov’s hometown of Nizhny Novgorod.