The wife of the late Russian opposition leader Alexei Navalny has said he was killed by poisoning while serving a prison sentence in an Arctic penal colony in 2024.

In a video shared on social media, Yulia Navalnaya said analysis of smuggled biological samples carried out by laboratories in two countries showed that her husband had been murdered.

She did not provide details on the poison allegedly used, on the samples or on the analysis – but challenged the two laboratories to publish their results.

Navalny – an anti-corruption campaigner and Russia's most vociferous opposition leader - died suddenly in jail on 16 February 2024 at the age of 47.

In 2020 he was poisoned with a Novichok nerve agent and almost died. He underwent treatment in Germany, and was arrested at the airport upon his return to Russia.

At the time of his death he had been in jail for three years on trumped-up charges and had recently been transferred to a penal colony in the Arctic Circle.

Navalny's supporters and colleagues at his Anti-Corruption Foundation (FBK) have always maintained the Russian government was involved in his demise.

Navalnaya said that after her husband's death in February 2024, his team were able to obtain and securely transfer biological samples abroad and that two laboratories in different countries had concluded he had been poisoned.

She did not share the location of the laboratories - but she implied that they were not making their findings public due to political considerations.

They don't want an inconvenient truth to surface at the wrong time, she said.

Navalnaya also suggested she would get pushback on trying to investigate her husband's death further: 'You are the wife, of course, but there is no criminal case, there are no legal grounds to hand documents to you.'

But I have grounds. Not legal, but moral grounds.

She added that Navalny had been her husband, friend and closest person – and a symbol of hope for a better future for our country.

I know he was a symbol to you too, she said over images of Navalny's Moscow funeral which drew thousands despite warnings from the authorities not to attend.

I will not be silent. I affirm that Vladimir Putin is guilty of killing my husband, Alexei Navalny... I urge the laboratories which conducted studies to make the results public.

On Wednesday Kremlin spokesman Dmitry Peskov said he was unaware of Navalnaya's statements.

According to her, on the day Navalny died, he was taken out for a walk but felt ill. When he was taken back to his cell, he began to have convulsions and vomited, allegedly while being observed by prison guards.

Navalny's associates have shared previously unseen images on social media purporting to show his cell on the day he died and the tiny exercise yard where he was allowed out.

The Kremlin has not responded directly to the claims, and it remains speculative regarding any further investigation into Navalny's passing. As a prominent opposition figure, Navalny's life and death have sparked ongoing debates about freedom and human rights in Russia, with his widow vowing to continue advocating for justice.