Roman Dobrokhotov had been content enough for his appearance at a conference in Washington DC this week to be publicised, although it was not something he would normally risk in Europe. The dissident Russian journalist was named during a trial in London last year as one of the targets of a Russian spy ring that appeared to have murderous intent.

“Maybe burn him alive on the street, spray him with some super-strong acid, VX, like the North Koreans, or the ricin,” a Russian-hired operative had texted of the plans for Dobrokhotov in Britain.

American soil, though, has traditionally been regarded as something of a safe place for those speaking out against the Kremlin, whether it has been under the red flag of the Soviet Union or the tricolour of Vladimir Putin’s Russian Federation. It might be possible for Kremlin agents to get away with deploying poison-tipped umbrellas on people crossing London’s Waterloo Bridge, as was the fate of the Bulgarian dissident Georgi Markov in 1978, but risking such colourful assassinations on the Brooklyn Bridge or indeed anywhere on US territory would be a different matter entirely.

If not part of the so-called Moscow rules, the fabled operating guidelines for western and Russian spies, then there was certainly an adjunct, a gentleman’s agreement of sorts, that neither side would kill on each other’s soil. That had been the understanding of many of the other dissidents as they prepared to appear at the Washington Dialogue conference on Russian affairs being held in the high-rise office of the National Endowment for Democracy, a short walk from the White House.

This week the kaleidoscope was shaken. “It looks like starting from today, the rules have changed in America,” Dobrokhotov, 43, said. “We will have to change how we behave there. Nowhere is safe.”

The game changer overshadowing the Washington conference was an announcement on Tuesday that the US Department of Justice was unsealing indictments in absentia against five individuals allegedly working for Russia’s intelligence services who were said to have conspired to “conduct attacks and murders around the world, including in the United States”.

The most eye-catching claim was that of an audacious plot to recruit unnamed US residents to “eliminate” a prominent Russian dissident living in the US capital. Those named as part of the spy network were a serving officer of the Russian Federal Security Service (FSB), Kirill Khrameev, 27, and his father, Yuri Khrameev, 63, who is a former FSB colonel, along with two 35-year-old Cubans, Oemis Romagoza Durruthy and Yaidel Delgado Suarez, nicknamed “the Viking”, and a 22-year-old Venezuelan, Angel Eduardo Castro.

The FBI had uncovered encrypted messages – written in Spanish and ineptly shrouded in spy code – commissioning what one of the alleged ring members had described as “gravely serious work”: an offer of $40,000 (£30,000) to surveil and then kill someone in Washington that the Russian state wanted to “disappear”.

There was talk of bringing in assassins from Mexico to carry out the “construction” (the word used by the agents for murder) but they were “delayed” and so a local killer was sought, according to the indictment. The identity of the purported victim was not revealed by the authorities, but among the rumoured potential targets was Vladimir Kara-Murza, who was freed from jail in Siberia and went to the US as part of a swap for Russian intelligence operatives in 2024. He declined to comment on the case when approached by the Guardian.

The almost unprecedented nature of the plot on US soil was unintentionally highlighted in the indictment itself, which listed a series of assassinations carried out by the Russian intelligence services. There was Paul Klebnikov, an American journalist and historian, murdered in Moscow in 2004. Two years later, Alexander Litvinenko, a former FSB officer, was killed in London by two Russian agents who put radioactive material in his tea. In 2018, Sergei Skripal, a former Russian military intelligence officer, and his daughter, survived after being poisoned with a military-grade nerve agent in Salisbury in the UK; a local woman, Dawn Sturgess, died after being contaminated. In 2019, a court in Germany found that Zelimkhan Khangoshvili, a former commander in the second Chechen war, was assassinated in Berlin, on the order of the Russian state. And in 2024 Alexei Navalny, the Russian opposition leader, died while in custody after being previously poisoned with the nerve agent Novichok while outside the country.

“More recently, countries throughout Europe have accused Russia of sabotage operations and extrajudicial targeting,” the indictment goes on. “For example, in or about September 2026, a German investigation reportedly linked the GRU’s military intelligence services to a drone attack at the Leipzig/Halle airport in Germany.”

But no such activities on US soil were raised in the paperwork, and for historically rooted reasons.

“I would describe it as an unwritten set of cold-war rules of the road,” said Chris Costa, a former US intelligence chief who is today executive director of the International Spy Museum in Washington DC. “The US and Soviet Union conducted aggressive espionage against one another, but there were understood limits, particularly around physically targeting each other’s intelligence personnel and families … If these allegations are proved, directing surveillance and murder on US soil crosses a very different line from traditional espionage.”

Why would the Russians cross this red line? Jack Devine, a former associate director of operations at the CIA, said that the Kremlin had perhaps become blase about the potential repercussions – but that it could prove to be a misstep.

“The Russians today put far less weight on political criticism internationally, and are less concerned about the ramifications, including sanctions,” he said. “Putin has a vision of himself in Russia and in the world as a powerful leader of the old school which he has often reminisced about in his interviews and public statements. I believe it’s wrongfooted, and he may be underestimating the long-term internal and external ramifications of this isolation.”

For Calder Walton, author and assistant director of the Belfer Center’s Intelligence Project at Harvard University, it is not just the Russian motivations that should be analysed. In 2023, Walton revealed in his book Spies that three years earlier a Russian assassination squad had targeted Aleksandr Poteyev, a defector who had been living in the US.

“In the Poteyev episode, American authorities apparently chose secrecy, presumably to protect intelligence sources and methods and avoid a public confrontation with Moscow,” he said. “By unsealing this indictment, the justice department is doing something different: exposing the alleged network, warning potential recruits, reassuring threatened dissidents and imposing costs on individuals who might otherwise have continued to operate in the shadows. Public attribution is itself a counterintelligence weapon.”

European diplomats in Washington tasked with monitoring the conflict in Ukraine and US-Russian relations also said the exposure of the plot by the FBI indicated a shift in Washington’s position. “It’s a big deal that the US chose to reveal this now,” one said. “The decision to do that raises the profile and shows the clear and imminent threat to dissidents in the US.”

Walton added: “The immediate policy consequences may be limited because all five defendants are reportedly abroad and remain at large.

“We should nevertheless expect greater protection for Russian dissidents and defectors, intensified investigation of Russian proxy networks, closer intelligence cooperation with European allies, and potentially further sanctions, expulsions or criminal charges.”

Evidence of a heightened state of alert to the risk to dissidents in the US has already emerged. Anastasia Shevchenko, a vocal critic of Putin who fled Russia for Lithuania in 2022 after becoming the first person found guilty of breaking a new law of participating in an “undesirable organisation”, said she had been warned at a recent interview for a visa to the US that she could not assume that she would be safe during her visit.

Nikkie Lyubarsky, a research associate at the Soufan Center, an NGO in New York specialising in global security, said the unsealing of the indictment could reflect a “behind the scenes” escalation in tension between the White House and the Kremlin as a result of Russia’s reported support for Iran in the continuing conflict with the US and Israel.

“The US publicising [the indictments] now definitely raises some flags in my mind,” said Lyubarsky. “It coincides obviously with the sanctions that have just been passed in the House and the CIA director’s visit to Russia recently. There’s probably some sort of escalation behind the scenes that we’re not aware of. It could be tied to Russian intelligence-sharing with Iran. That would be my best guess.”

Back at the Washington Dialogue conference, the perhaps understandably conspiratorial-minded dissidents chewing on sandwiches at the lunch break had their own theories. Was Donald Trump seeking to distance himself from the news that the wedding of his son, Donald Trump Jr, had been partly paid for by the Putin loyalist and oligarch Umar Kremlev?

Natalia Arno, the founder and president of the Free Russia Foundation, who experienced symptoms from a suspected poisoning during a 2023 trip to Prague that she believes was commissioned by the Kremlin, said that for all the theorising, one thing had changed undeniably. “We thought the Kremlin wouldn’t be as brazen as to do something on United States soil,” she said. “It’s a different landscape.”