An ally of late opposition leader Alexei Navalny said that Russian authorities have given his mother a deadline to agree to forgo a public funeral or else they will bury him on prison grounds.

Lyudmila Navalnaya was given three hours to accept a proposal for a private funeral outside the public eye, Mr Navalny’s close associate Ivan Zhdanov said on social media, in what appears to be another dark twist in the almost week-long stand-off with the authorities to retrieve the politician’s body.

Mr Navalny, 47, Russia’s most well-known opposition politician, unexpectedly died last Friday in an Arctic penal colony, prompting hundreds of Russians across the country to stream to impromptu memorials with flowers and candles.

The Russian authorities have detained scores of people as they seek to suppress any major outpouring of sympathy for President Vladimir Putin’s fiercest foe before the presidential election he is almost certain to win.

Mr Navalny’s mother and lawyers have been trying to retrieve his body since late last week – drawing support in those efforts from prominent Russians – but have faced resistance from the authorities.

Ms Navalnaya said on Thursday that investigators allowed her to see her son’s body in the morgue in the Arctic city of Salekhard.

She said she repeated her demand to have Mr Navalny’s body returned to her and protested against what she described as authorities trying to force her to agree to a secret burial.

“They want to do it secretly without a mourning ceremony,” she said.

Mr Navalny’s spokesman, Kira Yarmysh, said on X, formerly Twitter, that his mother was also shown a medical certificate stating that the 47-year-old politician died of “natural causes”.

Posting on social media, prominent Russians have appealed directly to Mr Putin to demand that he return Mr Navalny’s body to his family.

“Just give Lyudmila her son,” said Nobel Prize-winning journalist Dmitry Muratov. “It’s awkward to talk about this in a country that still considers itself Christian.”

Nadya Tolokonnikova, who became widely known after spending nearly two years in prison for taking part in a 2012 protest with the band Pussy Riot inside Moscow’s Christ the Savior Cathedral, also released a video.

“We were imprisoned for allegedly trampling on traditional values. But no one tramples on traditional Russian values more than you, Putin, your officials and your priests who pray for all the murder that you do, year after year, day after day,” Ms Tolokonnikova said.

“Putin, have a conscience, give his mother the body of her son,” she added.

Ballet star Mikhail Baryshnikov said he “firmly requests” authorities return “the body of the murdered Alexei Navalny to his mother”.

Mr Navalny’s mother has filed a lawsuit at a court in Salekhard contesting officials’ refusal to release her son’s body.

A closed-door hearing has been scheduled for March 4. On Tuesday, she appealed to Mr Putin to release her son’s remains so that she could bury him with dignity.

In a video on Monday, Mr Navalny’s widow, Yulia Navalnaya, accused Mr Putin of killing her husband and alleged the refusal to release his body was part of a cover-up.

Kremlin spokesman Dmitry Peskov rejected the allegations, calling them “absolutely unfounded, insolent accusations about the head of the Russian state”.