Russian opposition leader Alexei Navalny was killed by poison from a South American frog, claim Great Britain and some of its European allies.
In samples taken from Navalny's body, which was in a remote penal colony in Russia at the time of his death, traces of epibatidine were found, which is believed to have led to his death in a Siberian penal colony two years ago, the British Foreign Office said.
Western allies said that only the Russian state had the "means, motive and opportunity" to use such a deadly toxin.
The Kremlin dismissed the allegations as "part of a media war and propaganda campaign."
Alexei Navalny died on February 16, 2024., in a prison in a remote area near the Arctic, where he was serving a long-term prison sentence.
The state prison service said at the time that he died of "sudden death syndrome."
What is epibatidine?
A natural neurotoxin isolated from the skin of the Ecuadorian poison dart frog (Ecuadorian poison dart frog), says toxicologist Jill Johnson.
It is "200 times more powerful" than morphine, she told the BBC in Russian.
Epibatidine occurs naturally in poison dart frogs in South America, but can also be produced in the laboratory.
Frogs in captivity do not produce this poison, and it cannot be found naturally in Russia, the statement from Britain and its European allies said.
Among the species that secrete this poison through their skin are Anthony's poison frog (Anthony's poison arrow) and the phantom poison frog (Phantasmal poison frog).
Although epibatidine has been investigated as a potential painkiller and for the relief of painful inflammatory lung diseases, it is not used in clinical practice due to toxicity.
How does frog venom work?
This powerful chemical compound acts on nicotinic receptors in the nervous system, Johnson explains.
Because it overstimulates these nerve receptors, if dosed correctly it can cause muscle twitching, paralysis, seizures, slowed heart rate, respiratory arrest, and ultimately death.
Its effects can also lead to respiratory blockage and "any person poisoned in this way dies of suffocation," said Alastair Hay, professor of environmental toxicology at the University of Leeds.
If the poison is found in someone's blood, "it indicates intentional administration," he added.
Epibatidine toxicity can even be "enhanced by the concomitant administration of certain other drugs, and such combinations have been investigated," Hay said.
How rare is this toxin?
Epibatidine is extremely rare and exists in only one geographic area and in very small quantities, Johnson says.
The frog referred to by British authorities is believed to be Anthony's poison frog, an endemic species that lives only in Ecuador and Peru.
They produce the poison by feeding on appropriate food that allows the formation of alkaloids - a type of organic compound - from which epibatidine is formed.
It then accumulates in their skin.
However, if the frog's diet changes, epibatidine stores are depleted.
"Finding a wild frog in the right place, eating exactly the food needed to make the right alkaloids, is almost impossible... Almost," Johnson said.
"This is an incredibly rare way of poisoning people - the only other cases of epibatidine poisoning I know of were linked to laboratories and were not fatal."
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What did Russia say?
European laboratories confirmed that Navalny died from this rare poison, it was announced on February 15, 2026.
Moscow previously claimed that Navalny died of natural causes, while his wife Yulia Navalny insisted that her husband was killed by poisoning.
The Russian embassy in London denied Moscow's involvement in Navalny's death and described the statement as "the small-mindedness of Western fabulists" and "necro-propaganda."
"All these conversations and statements represent an information campaign aimed at diverting attention from the West's pressing problems," Kremlin spokeswoman Maria Zakharova told the state-run TASS news agency.
Hamish de Breton-Gordon, a former senior British military and NATO officer and chemical weapons expert, said that everything the Kremlin says, including everything about Navalny's death, should be taken "with a grain of salt."
NATO members have "shown that they have evidence that Navalny was killed by the state," he told the BBC.
At the time of his death, Navalny had already been in prison for three years, and was then transferred to a penal colony in the Arctic.
An official notification sent to Lyudmila Navalny, Alexei's mother, stated that his death was registered on February 16, 2024, at 14:17 p.m. local time.
At the same time, prison services announced on their website that Alexei Navalny died after falling ill after a walk and "almost immediately losing consciousness."
He was usually taken for a walk around the prison yard, which is above the Arctic Circle in the Yamalo-Nenets Autonomous Okrug, as the politician himself wrote on Instagram, early in the morning, even before dawn.
During the day, the 47-year-old went out for a short walk, complained that he was not feeling well, then collapsed and never regained consciousness, Russian prison services said.
On February 15, 2024, Navalny participated via video link in a court hearing on one of his lawsuits against the colony's leadership.
A recording of the end of this meeting was published by SOTAvižn.
In the video, Navalny is joking and shows no signs of illness.
The day before, on February 14, he was visited by his lawyer, who said that "everything was fine" with Navalny.
Doctors tried to revive Navalny for half an hour, the Russian news agency Interfax reports.
Doctors were at his side for two minutes after he fainted, and an ambulance arrived within six minutes, according to prison authorities.
Watch the video: Navalny's last video before his death
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