Barricades were lowered near the church where Navalny's memorial will be held on Friday
With Alexey Navalny's funeral hours away, his team say they continue to face difficulties in organizing a farewell ceremony.
His spokeswoman Kira Yarmish said they were unable to find a mortuary to transport the body to the church.
“Unknown people are calling the morgues and threatening them if they agree to take Alexey's body,” Ms Yarmish said.
A funeral is scheduled to take place on the outskirts of Moscow on Friday – two weeks after he died in an Arctic prison.
On Wednesday, the memorial service will be held at 14:00 Moscow time (11:00 GMT) at the Church of the Icon of Our Lady Quench My Sorrows in Marino, the group announced.
Burial will then take place at the nearby Borisovskoye Cemetery at 16:00.
The funeral will also be webcast on Navalny's YouTube channel.
Navalny died on February 16 in a Russian prison inside the Arctic Circle. He spent three years in prison on trumped-up charges.
Navalny died on February 16 in his cell at a prison colony in Siberia, where he was serving a 19-year sentence on charges widely seen as politically motivated.
His team – who encouraged people to attend – shared a map of the route between the two locations.
They also shared a list of locations overseas — from Seoul to Rome, Montreal and Stockholm — where people could attend Navalny's memorial services.
It is unclear how many people will attend Friday's funeral in Moscow.
Navalny's former chief of staff, Leonid Volkov, told BBC Newshour that he was worried about what would happen during the service in Moscow.
“I'm afraid surprises are expected tomorrow. Frankly, as I speak now, I don't know if they really let people say goodbye to Alexei,” he said.
He said Navalny's team was also concerned that there could be problems at the church where the service is held.
In March 2015, thousands took to the streets to pay tribute to slain opposition politician Boris Nemtsov, but public expressions of grief for President Vladimir Putin's opponent are now unlikely to be allowed.
In recent years, Russian authorities have cracked down on any activity that could be interpreted as criticism of the government. Attempts to commemorate Navalny's death have been met with violent responses, with makeshift memorials removed and hundreds arrested.
Photos circulating on social media Thursday afternoon showed a heavy police presence and barricades being erected near the church where the memorial will be held and at the cemetery where Navalny will be buried.
Telegram channel Rusnews said surveillance cameras were installed on “every streetlight” around the cemetery.
The First Department – a group of lawyers and human rights defenders – shared advice on social media for those planning to attend Navalny's funeral.
It warned of “pro-government activists” acting as provocateurs and urged people to be vigilant: “Detention after the ceremony cannot be ruled out… Stay under the radar of the security forces – don't use public transport or apply for documents. A few days after the funeral.”
The advice also includes not carrying any items with a photo of Navalny or the logo of his anti-corruption foundation, which has been designated a terrorist organization by Russian authorities.
It is not known which members of Navalny's family will be able to attend the funeral, apart from his mother Lyudmila, who recently publicly accused authorities of withholding her son's body.
Navalny's children Daria, 23, and Jagar, 15, live abroad.
His widow, Yulia, is not currently believed to be living in Russia, but is at risk of arrest if she returns because of her work with Navalny's group and her recent public statements blaming Russian President Vladimir Putin for her husband's death.
Authorities reportedly tried to thwart attempts by Navalny's team to organize a public farewell ceremony for the opposition leader for several days.
On Tuesday, Ms Yarmish said Navalny's team was struggling to find a place to host the ceremony. Some funeral homes claimed they were fully booked, while others were “restricted” from working with them, he said.
In a speech on Wednesday, Navalny's widow, Yulia, said she did not know whether the funeral would be peaceful or whether police would arrest those who came to say goodbye.
