The alleged poisoning of Russia’s best-known opposition leader Alexei Navalny is the latest to occur for a long line of Kremlin opponents.

The Kremlin, as it did in Navalny’s case, denied any involvement, but the poison has long been a weapon used by Russian security services and employed by the Soviet Union under President Vladimir Putin.

In some cases, evidence has emerged that seems to link them strongly to the Russian state, while others have remained a mystery.

Kremlin spokesman Dmitry Peskov told reporters on Monday that he did not agree that there was a “trend” of poisoning Kremlin opponents.

“You will agree that in many countries of the world there is a lot of poisoning happening every day,” Peskov said, saying it was necessary to look at each case individually.

But the list of those who worried the Russian government or the security services and then suffered poisoning is long.

During its early years, the Soviet Union developed a secret poison laboratory within its security services. The laboratory, known among security officers as “kamera” – which means “the chamber” in Russian – has specialized for decades in the development of difficult-to-detect poisons and, under Joseph Stalin, has tested its products on Gulag prisoners, according to Soviet defectors.

Boris Voldarsky, a former officer of the Soviet military intelligence agency, GRU, who wrote a book on the KGB poison control program wrote that there is a constant in the lab’s products.

“They must make the victim’s death or illness appear natural or at least produce symptoms that will baffle doctors and forensic investigators.” To this end, Kamera has developed its defining specialty: combining known poisons in original and untraceable forms, ”Voldarsky wrote in an article for the Wall Street Journal in 2005.

There were several famous poisoning episodes during the Cold War. Georgi Markov, a Bulgarian dissident, died after a KGB agent stung him with a ricin-tipped umbrella. In 1957, Nikolai Khokhlov, a KGB defector, came close to death after drinking a cup of coffee containing an unknown type of thallium.

Poisonings have occurred under Putin almost since the start of his reign. In 2004, Viktor Yushchenko, a candidate who ran against an incumbent Kremlin-favored president for the Ukrainian presidency was poisoned with dioxin, leaving him disfigured.

In the same year, famous investigative journalist Anna Politkovskaya suddenly fell ill and passed out after drinking a cup of tea as she flew to the Russian city of Beslan during the school siege. She survived, but was shot two years later on Putin’s birthday.

The two poisonings that most closely associated Putin with international poisoning occurred in the UK In 2006 Alexander Litvinenko, a former FSB Russian security service officer turned critic, died after being exposed to polonium-210 , a radioactive isotope, slipped into her tea in an upscale hotel. British police then sought to indict two Russians, Dmitry Kovtun and Andrey Lugovoy, and a British public inquiry concluded that Putin probably personally ordered the assassination. Russia refused to extradite the two men and Lugovoy was appointed a member of parliament instead.

In 2018, another former Russian intelligence officer, Sergey Skripal, was nearly fatally poisoned by a nerve agent in the English town of Salisbury. The poison, which was identified by British investigators as a nerve agent, known as “Novichok”, developed by the Soviet Union as part of a secret chemical weapons program. Russia again denied responsibility, but British police were able to track down two men, who were later identified as Russian military intelligence officers. The two men, Anatoly Chepiga and Alexander Mishkin, have already received Russia’s highest state honor, personally awarded by Putin.

Experts pointed out that Navalny may not have been poisoned by order of the Kremlin. Navalny, who has made a name for himself with high-profile investigations into allegations of corruption among powerful Russians, has many enemies.

However, the choice of poison usually means the involvement of Russian security services, whether acting for the state or out of corruption for others.

“It doesn’t matter whether it is an attempted murder or just fear-mongering tactics, poisonings are almost always linked to the security services,” Tatiana Stanovaya, a non-resident academic at the Carnegie Moscow Center, wrote last week, adding that she did not believe The Kremlin ordered the assassination attempt. She wrote that she believed the attack on Navalny was likely carried out by powerful figures acting on their own initiative, either indifferent to the Kremlin’s reaction or believing it would please her. .

Navalny’s case has so far drawn the closest comparisons with two other suspected cases of poisoning of opposition figures. Vladimir Kara-Murza, a pro-democracy activist from Open Russia, a group funded by Putin’s enemy Mikhail Khodorkovsky, twice nearly died in 2015 and 2017 after his organs suddenly began to fail. A French laboratory found high levels of heavy metals in his blood but could not identify the poison.

Two years ago, Petr Verzilov, a member of the protest group Pussy Riot, suddenly fell inexplicably and seriously ill. He was evacuated to Germany for treatment, kept in an induced coma, and doctors said he was poisoned. Verzilov survived, and last week he helped organize the airlift of Navalny to Germany by the same Berlin-based non-profit organization that had helped him.

Verzilov said his symptoms were very similar to Navalny’s and personally blamed Putin for both poisonings.

The Charité hospital treating Navalny said his analysis showed he was suffering from intoxication with cholinesterase inhibitors, chemicals that belong to a very wide group of substances ranging from pesticides and drugs to nerve agents. military grade, which includes Novichok.

Dan Kaszeta, a chemical and biological weapons expert and author of a book on nerve agents, “Toxic,” told ABC News on Tuesday that without knowing what substance it was at the moment, it was impossible to tell. tell if what had poisoned Navalny had been developed. in a fancy military lab or something more commonly available.

Andrei Soldatov, a longtime Russian security service expert and author of “Compatriots,” a story of Russian espionage abroad, including poisonings, said he did not believe a character having Navalny’s position in Russia could have been targeted without the Kremlin. order.

“I’ve heard this argument for many years. From Politkovskaya, to Litvinenko, to Skripal. That it couldn’t be the Kremlin but someone trying to please the Kremlin,” Soldatov said by telephone on Wednesday. “But the problem with this argument is that in 2020 the situation is not what we had in 2004, 2006. The room for any kind of unauthorized secret service activity, especially in such a sensitive area, is very limited. It’s really hard to imagine that someone would dare to do something so drastic and not get some sort of agreement first. To be sure that he or she is on the safe side. “