Yulia Navalnaya, the widow of Russian opposition leader Alexei Navalny, has called for an election day protest against President Vladimir Putin.
As part of the protest, people should form long queues at polling stations on 17 March at midday, Ms Navalnaya said.
“We need to use the election day to show that we exist and there are many of us,” she said in a video message.
Ms Navalnaya’s husband died suddenly at a Russian penal colony on 16 February. She has blamed Mr Putin for his death.
Her call for a polling day protest has been dubbed “Midday against Putin”.
Russia’s presidential election – which most international observers do not believe will be free or fair – will take place from 15 to 17 March. Mr Putin is widely expected to win a fifth term in office.
Ms Navalnaya said turning up at polling stations at the same time was a “very simple and safe action” that could not be prohibited by the authorities, but would allow like-minded people to “see that there are many of us and we are strong”.
People can then vote for any candidate except President Putin, spoil their ballot or write “Navalny” in big letters, Ms Navalnaya said.
The idea of a midday gathering at polling stations was put forward by Navalny two weeks before his death.
Navalny – who continued to keep up a social media presence from jail through messages posted by his lawyers – wrote on X that the election day protest had the chance to be a real “all-Russian protest action… available to everyone, everywhere.”
“Millions will be able to take part in it. And tens of millions will witness it,” Navalny wrote.
Navalny himself was barred from running in the 2018 presidential vote because of an embezzlement conviction widely condemned as politically motivated.
He died while serving a lengthy prison sentence on politically motivated charges.
The Kremlin has said the 47-year-old died of natural causes, but his supporters and many foreign leaders have blamed Mr Putin for his fate.
Ms Navalnaya stepped into the political spotlight soon after husband’s death was announced, and has since addressed the European Parliament and held talks with US President Joe Biden.
In her YouTube message, she spoke of being heartened by the large crowds that came out last week for her husband’s funeral in Moscow.
Since last Friday, thousands of people have continued to turn up to Borisovskoye Cemetery, and Navalny’s grave has been submerged by flowers. “I can’t tell you how much that has meant to me,” Ms Navalnaya said.
“Alexei dreamed of the beautiful Russia of the future – and that is you,” she added.
