The Russian authorities have transferred the body of the opposition leader Aleksei A. Navalny to his mother, his spokeswoman said on Saturday, ending a grim battle for custody of his remains, but it is unclear whether he will get a funeral that the public can attend.

“Aleksei’s body has been handed over to his mother,” Mr. Navalny’s spokeswoman, Kira Yarmysh, said in a statement posted on social media. “The funeral is yet to come. We don’t know whether the authorities will interfere with carrying it out in the way the family wants and as Aleksei deserves.”

Mr. Navalny’s mother, Lyudmila Navalnaya, on Saturday was still in the northern city of Salekhard, near the Arctic prison where Mr. Navalny was reported to have died on Feb. 16, Ms. Yarmysh said. She added that the opposition leader’s team would release information about the funeral “as it becomes available.”

Mr. Navalny’s family and aides have accused the Russian authorities of keeping his body hostage and “blackmailing” his mother into agreeing to bury him in secret. On Friday, Ms. Yarmysh said that officials in Salekhard had given Ms. Navalnaya an ultimatum demanding that she assent to such a secret funeral within three hours, or else that he would be buried on prison grounds.

That deadline passed on Friday evening without any new information from Mr. Navalny’s aides. The Russian authorities have not commented on the Navalny team’s version of events.

The circumstances of Mr. Navalny’s death remain unclear, and it was not immediately evident whether his family would seek to conduct an independent autopsy before his burial. According to Ms. Yarmysh, Ms. Navalnaya received a medical report earlier this week that said he had died of natural causes.

The news that Ms. Navalnaya, 69, received custody of the body suggested that the Russian authorities had relented after a dayslong social media campaign by Mr. Navalny’s team. On Saturday, Mr. Navalny’s widow, Yulia Navalnaya, 47, released a six-minute YouTube video denouncing President Vladimir V. Putin of Russia for maligning the Christian values he professes as he “mocks Aleksei’s mother and forces her to agree to a secret funeral.”

“This is some kind of Satanism, paganism,” she said. “What are you planning to do with his body?”

The Navalny team’s social media accounts also shared videos of Russian celebrities like the ballet star Mikhail Baryshnikov calling on the Kremlin to release Mr. Navalny’s remains.

“Thanks to all who posted and recorded video messages,” a top Navalny aide, Ivan Zhdanov, said on the Telegram social messaging app. “You all did what you should have done.”

The question now is how Mr. Navalny’s funeral will take shape. The dispute over custody of his body appears to reflect the Kremlin’s fears about a public funeral in Moscow turning into a focal point for protest.

Last August, the authorities in St. Petersburg orchestrated a secret burial of the mercenary leader Yevgeny V. Prigozhin, who died in a plane crash after leading a 24-hour revolt and marching on Moscow. But Mr. Navalny’s family and aides have declared that they will not accept a quiet burial, signaling they will try to turn the opposition leader’s funeral into a rare show of dissent inside Russia.

Mr. Putin “is not allowing people to say farewell to Aleksei,” Mr. Navalny’s longtime chief of staff, Leonid Volkov, said in a video posted online Friday.

“I am surprised that he is not thinking about how he himself will be buried,” Mr. Volkov added, referring to the Russian president. “In his place, I would think about it.”

In trying to build momentum for a public funeral, the Navalny team appears to be following the direction of their dead leader, who had urged his supporters to keep fighting if he were ever killed. In a widely circulated clip from an interview for the 2022 “Navalny” documentary, Mr. Navalny says that if he is killed, “you are not allowed to give up.”

“If they decide to kill me, it means that we are incredibly strong,” he says. “We need to utilize this power to not give up.”

The Navalny team’s Saturday announcement about the transfer of his body came on the second anniversary of the start of Russia’s full-scale invasion of Ukraine. Many Ukrainians have long criticized Mr. Navalny — and his widow, Ms. Navalnaya — for not being sufficiently vocal in endorsing Ukraine’s sovereignty.

But Ms. Navalnaya did refer to the war in her video on Saturday, declaring that Mr. Putin and his officials would someday answer “for the war you started two years ago.”

Mr. Putin and his allies say “that you’re fighting some Western evil that interferes with our traditional values,” she said. “But you just kill. You just bomb sleeping civilians at night.”