The mother of late Russian opposition leader Alexei Navalny urged Russian President Vladimir Putin to hand over the body of her son in a video released on Tuesday.

Lyudmila Navalnaya: 'I demand that Alexei's body be released immediately'    

"I appeal to you Vladimir Putin, because the solution to this problem depends only on you," Lyudmila Navalnaya said dressed in black outside of the Arctic prison camp where her son had been been bars. 

"Let me see my son. I demand that Alexei's body be released immediately so that I can bury him in a humane way."

Navalny's team, citing Russian investigators, said the late opposition leader's body would not be handed over for 14 days, pending a chemical investigation.  

Western countries and Navalny backers, including his wife, have pinned the blame on Putin for Navalny's death. 

US vows 'major sanctions' on Russia 

The US plans to unveil a "major sanctions package" on Friday to "hold Russia accountable for what happened" to Navalny, National Security Council spokesman John Kirby told reporters on Tuesday.

Kirby added that sanctions would also be in response to Russia's "actions over the course of this vicious and brutal war that has now raged on for two years."

The French Foreign Ministry on Tuesday said it "holds the Russian authorities fully responsible for the death of Alexei Navalny," while calling for "an independent and in-depth investigation."

France also urged the release of all political prisoners in Russia and "expresses in particular its deep concern over the critical state of health of opponent Vladimir Kara-Murza."

Journalist and activist Kara-Murza has been sentenced to 25 years in prison in Russia. Putin critic and Kara-Murza's close friend Bill Browder told DW last week during the Munich Security Conference that he was "terrified for his safety and for his well-being."      

Meanwhlie, Poland also escalated its criticism of Russia and summoned Russia's ambassador.

"The ministry called on Russian authorities to take responsibility for the death of Alexei Navalny and conduct a full and transparent investigation to determine the circumstances and cause of his death," the Polish Foreign Ministry said.  

Poland said the "authorities of the Russian Federation demonstrate a complete rejection of moral norms not only in the context of dealing with domestic civil society, but also in the ongoing war against Ukraine."

In addition, Slovenia announced that it was summoning the Russian ambassador on Tuesday.  

wd/nm (Reuters, AFP)