Alexei Navalny's widow has paid tribute to the Russian opposition leader on the one year anniversary of his unexpected death.

Hundreds of people risked arrest and freezing weather in Moscow on Sunday as they queued to visit Navalny's grave and lay flowers, light candles and honour his memory.

Dissident Navalny died mysteriously at the age of 47 on February 16 last year in a 'special regime' penal colony known as 'Polar Wolf' above the Arctic Circle.

His widow Yulia Navalnaya wrote online: 'I used to think that the phrase "a year has passed and there hasn't been a day I didn't remember" was total nonsense. And it turned out that this is not nonsense.

'A year. The whole year and there was not a single day that I didn't think about Alexei. I didn't laugh with him, didn't consult him, didn't argue with him.'

The politician, who campaigned against official corruption and led major anti-Kremlin protests, was serving a 19-year sentence on charges of extremism.

Russia has never fully explained his death, stating merely that Navalny had felt unwell after a walk and lost consciousness.

An ambulance arrived to try to save him to no avail, the Federal Prison Service said in a statement at the time.

Speaking at the Munich Security Conference just hours after the news of her husband's death broke one year ago, Navalnaya expressed her scepticism at the information from Russian government sources.

'We cannot trust Putin and the Putin government. They always lie,' she said, solemn and tearful.

'But if this is true, I want Putin, his entire entourage, Putin's friends, his government to know that they will bear responsibility for what they did to our country, to my family, to my husband. And this day will come very soon.'

Supporters have helped select a new design for a memorial to Navalny at the Borisovskoye cemetery.

The winning entry, Called 'Titan and Stone', is a tombstone comprised of three blocks of black granite and a metal inscription with Navalny's name in capital letters.

His mother Lyudmila Navalnaya joined mourners yesterday to visit his grave and his widow was due to address a memorial ceremony in Berlin, where she is living in exile.

The German chancellor, Olaf Scholz, paid tribute to Navalny, saying Putin's most significant challenger to date had died 'because he fought for democracy and freedom in Russia'.

Scholz said: 'Putin 'brutally combats freedom and its defenders. Navalny's work was all the more brave.

'His courage made a difference and reaches far beyond his death.'

And the EU's foreign policy chief Kaja Kallas said Putin bore 'ultimate responsibility' for Navalny's death.

He added: 'Navalny gave his life for a free and democratic Russia. As Russia intensifies its illegal war of aggression against Ukraine, it also continues its internal repression, targeting those who stand for democracy.'

Navalny's sudden death came less than a month before a presidential election that extended Vladimir Putin's rule of more than two decades.