The stalling over the funeral is believed to be an effort to avoid a large showing of public support that could embarrass the Kremlin.
Alexei Navalny’s mother has said she was given an ultimatum to agree to a secret funeral within three hours or else her son would be buried at prison.
Lyudmila Navalnaya said she refused to negotiate with investigators because “they do not have the authority to decide how and where she should bury her son”, according to a Navalny spokeswoman.
Ms Navalnaya wants “compliance with the law” and authorities are “obliged to hand over the body within two days of establishing the cause of death”, said Kira Yarmysh.
“According to the medical documents she signed, these two days expire tomorrow,” added the spokeswoman.
“She insists that the authorities allow the funeral and memorial service to take place in accordance with normal practice.”
The update was posted on X on Friday afternoon and it’s unclear if authorities have acted on the ultimatum.
The campaigner and politician died a week ago but authorities have denied foul play and say he fell ill after going for a walk at his penal colony in Arctic Russia.
His death certificate cited “natural causes”, according to Mr Navalny’s team.
However, his wife believes he was poisoned with novichok – the same nerve agent used in an alleged assassination attempt against him by Russia in 2020.
Mr Navalny’s death has sparked severe condemnation of Russia by the West, and on Friday the US revealed more than 500 new sanctions.
The stalling over funeral arrangements is believed to be an effort to avoid a large public event that could feature protests and embarrass the Kremlin.
Lyudmila Navalnaya said in a YouTube video on Thursday that she had finally been allowed to see her son’s body but accused authorities of “blackmailing” her.
She said they had told her “time is not working for you” and suggested the body was “decomposing”.
“Looking into my eyes, they say that if I do not agree to a secret funeral, they will do something with my son’s body,” said Ms Navalnaya.
Mr Navalny, 47, was Vladimir Putin’s most vocal critic and the only opposition figure able to rally large numbers of people to take to the streets to protest.
He was serving a 19-year-sentence on charges his supporters say were designed to try and silence him.
Mr Navalny’s team are now offering €50,000 (£42,700) for “valuable and complete information about the murder of Alexei Navalny”.