Russian opposition leader Alexei Navalny officially announced on Tuesday his bid to run in the 2018 presidential election, a move that political observers say puts pressure on President Vladimir Putin and the Kremlin.

Mr Navalny said in a video statement posted on a new campaign website that “I will take part in the struggle for the post of president of Russia.”

Russia’s most widely-known opposition figure and a leading anti-corruption activist, Mr Navalny has repeatedly said that Mr Putin and his inner circle are guilty of graft and has successfully tapped into popular anger at the lavish lifestyle led by some of Russia’s elite.

Mr Navalny, 40, is currently on trial on fraud charges in a regional Russian city in a case that his supporters say is politically motivated. If convicted, he would be barred from running for public office.

Mr Putin hasn’t said whether he will seek a fourth presidential term in the March 2018 election, but he is widely expected to run.

Former Kremlin insider Gleb Pavlovsky said the announcement could push Mr Putin toward a decision to run because any other Putin-loyalist candidate would struggle to win against Mr Navalny.

“Navalny is not just announcing his intentions but throwing down a challenge to the current president,” Mr Pavlovsky told the Interfax news agency.

Mr Navalny said he would push to redistribute wealth, fight corruption, invest more in education and health, decentralise Russian politics, reform the country’s judiciary and pull back from involvement in foreign wars.

“It’s time for us to choose not only a person at elections. It’s time to choose between stagnation and a program of development,” Mr Navalny said in his video address.

The development received little coverage by state-owned television stations, which are almost universally pro-Kremlin and how most Russians get their news.

Experts said that Mr Navalny’s decision to launch a campaign was a shrewd political move that put the Kremlin off stride. Mr Navalny can now pressure authorities into allowing him to officially register his candidacy.

“Now everything that happens in the process going forward won’t happen in a vacuum, but will be an answer [to Mr Navalny's presidential bid],” political analyst Ekaterina Shulman wrote on Facebook.

Mr Navalny, a trained lawyer, heads the Anti-Corruption Foundation, which publishes extensive exposés about the personal wealth and alleged corruption of Russian officials.

But he has no experience in public office. He shot to prominence with his often-bitingly sarcastic blog entries about corruption among the Russian elite. He played a leading role in the massive anti-Putin demonstrations in 2011 and 2012.

In 2013, Mr Navalny organised a crowd-funded campaign to challenge Sergei Sobyanin, the incumbent pro-Putin candidate, in Moscow’s mayoral election. He surprised many observers by finishing in second place with almost 30 per cent of the vote.