Ex-tycoon Mikhail Khodorkovsky, who spent a decade in jail after challenging the Kremlin, openly stated his political ambitions on Saturday by announcing he would be ready, if called upon, to lead Russia in times of crisis.

By publicly voicing his readiness to take on the country's top job, the man who was once Russia's richest appears to have broken a promise to steer clear of politics which he made after being pardoned by President Vladimir Putin in December.

"I would not be interested in the idea of becoming president of Russia at a time when the country would be developing normally," he was quoted as saying by Le Monde newspaper.

"But if it appeared necessary to overcome the crisis and to carry out constitutional reform, the essence of which would be to redistribute presidential powers in favour of the judiciary, parliament and civil society, then I would be ready to take on this part of the task."

The comments were made as Khodorkovsky, 51, launched an online movement dubbed Open Russia to unite pro-European Russians in a bid to challenge Putin's grip on power.

"A minority will be influential if it is organised," he said during a ceremony broadcast online from Paris.

Khodorkovsky and his allies said political change could come quickly and insisted the time had come to think of Russia's future after Putin.

Khodorkovsky stressed that his project -- named after his eponymous charity that was shut down after his imprisonment -- would be an online "platform" for like-minded people, not a political party.

The Kremlin is still likely to find the project unsavoury, said the photogenic ex-tycoon sporting closely-cropped hair and a casual shirt.

"I expect him to be upset," Khodorkovsky said, referring to his nemesis Putin.

Russian activists and prominent emigres including Paris-based economist Sergei Guriyev and London-based businessman Yevgeny Chichvarkin -- both of whom fled the country under pressure from security services -- joined the online ceremony.

Khodorkovsky, who lives in Switzerland with his family, openly supported a Ukrainian uprising that ousted a Moscow-backed president in February, but indicated he did not want a bloody revolt for Russia.

The soft-spoken former head of the defunct Yukos oil firm -- who according to his allies was jailed for opposing the Kremlin -- said all those supporting a pro-European course for Russia should unite ahead of parliamentary elections scheduled for 2016.

Some analysts said they were surprised by Khodorkovsky's declaration of political ambitions.

Russian President Vladimir Putin in Sarov on September 19, 2014 Mikhail Klimentiev, Ria Novosti/AFP/File

-'Russia is Europe'-

The launch of his group comes as Kremlin critics say the country, locked in a confrontation with the West over Ukraine, is hurtling toward political and economic catastrophe.

The West and Kiev accuse the Kremlin of invading Ukraine and threatening the stability of Europe.

Russia's economy, already on the brink of recession, is reeling from several rounds of Western sanctions.

All major television stations in Russia are under state control and few at home can seriously challenge the Kremlin.

With prominent activist Alexei Navalny, 38, under house arrest, Russia's beleaguered opposition has been left rudderless.

But Khodorkovsky said everyday Russians can still influence the fate of their country.

"We support what they call the European choice or a state governed by the rule of law," he said.

"We believe that the statement 'Russia is not Europe' is a lie that is being imposed on society on purpose.

"This is being done by those who want to rule the country for life, those who want to spit upon law and justice," Khodorkovsky said in a thinly veiled reference to Putin, the former KGB operative who came to power in 1999.

"We are Europe, both in terms of geography and culture.

"We are not simply Russian Europeans. We are patriots. And true patriots even during pitch-dark reactionary times should serve their country and their people."

Putin, by comparison, has sought to promote Russia as an antithesis of the West and claimed isolation would be a boon for the country.

-'Long and dangerous path'-

Former Russian oil tycoon and Kremlin critic Mikhail Khodorkovsky arrives at the Wall Museum in Berlin to give a press conference on December 22, 2013 Clemens Bilan, AFP/File

Khodorkovsky's supporters expressed hopes his project would raise awareness among Russians and help them see through state propaganda.

"It is time to open our mouths," said Chichvarkin.

"We are ahead of a long, hard and dangerous path," added former deputy finance minister and economist Sergei Aleksashenko.

State media appeared to enforce a blackout on news coverage of Khodorkovky's online project.

His spokeswoman Olga Pispanen said the project's website, openrussia.org, became the target of distributed denial of service attacks.

Attempts to prevent activists from joining the ceremony were reported in the central Russian cities of Nizhny Novgorod and Yaroslavl.

While many scoffed at Khodorkovsky's effort to rally Russians while in exile, some said the project could pay off in the long run.

"Such a project is sorely needed," political analyst Mark Urnov said, calling it an "antidote" for the country's grim reality.