An undercover team working for Russia's Federal Security Service (FSB) followed opposition leader Alexei Navalny on more than 30 trips to and from Moscow since 2017 before he was poisoned in August, according to a bombshell investigation led by Bellingcat.

Why it matters: The Kremlin has denied having any role in the poisoning of Navalny, who is one of the most prominent domestic critics of President Vladimir Putin. But an analysis of "voluminous telecom and travel data" by Bellingcat suggests the poisoning with the nerve agent Novichok “was mandated at the highest echelons of the Kremlin."

Between the lines: "This investigation is particularly important due to the legal vacuum in which no country other than Russia – the country implicated in the assassination attempt – has offered its jurisdiction for an official investigation into Navalny’s near-fatal poisoning," Bellingcat writes.

Details: Bellingcat, an open-source journalism website that also identified the Russian officers behind the poisoning of former double agent Sergei Skripal in the U.K., found the attack was the culmination of years of stalking that began at least a month after Navalny's 2017 announcement that he would stand against Putin in presidential elections the next year.

• The investigation names two Russian doctors working with at least five FSB operatives who flew with Navalny at least 30 times over three years, and possibly attempted to poison him at least once before the August attack.
• Some FSB agents traveled to the hospital in the city of Omsk where Navalny was taken after the poisoning.

The big picture: In addition to detailing specific movements and calls made by the officers allegedly involved in the poisoning, Bellingcat's investigation also alleges that Russia is operating a clandestine chemical weapons program operating under the cover of an FSB investigative unit.

What they're saying: "Believe me when I say discovering Russia has a long running nerve agent based assassination programme targeting its most well known opposition figure was as much a shock to me as it is to you. How can governments across the world ignore this?" Bellingcat founder Eliot Higgins tweeted.

Go deeper:

• Read Bellingcat's full investigation
• Read CNN's version of the investigation