First, a warehouse in east London being used to supply aid to Ukraine burned down. Weeks later, an Ikea in Vilnius, Lithuania, mysteriously caught fire.

Swedish investigators were already looking into the possibility that several railway derailments could have been caused by a state-backed saboteur.

Then an inferno engulfed the largest shopping centre in Warsaw, Poland’s capital. It was Donald Tusk, the Polish prime minister, who began joining the dots to suggest the West was under attack by Russian espionage.

“We are examining the threads – they are quite likely – that the Russian services had something to do with the Marywilska fire,” he said last month.

His claims were further bolstered when a former Russian soldier was arrested north of Paris this week after explosives detonated in his hotel room.

Warnings from European intelligence agencies that Russia is plotting acts of sabotage on the Continent in its escalation of the stand-off with the Nato military alliance have been thrust into the limelight.

An intelligence assessment shared with Western governments claims that Russia’s notorious GRU military intelligence agency, known for its attacks on foreign soil using highly trained agents, is now turning to criminal gangs to carry out attacks in Europe.

The Kremlin’s spy network was dealt a blow in the weeks after Russia’s invasion of Ukraine on Feb 24 2022, when more than 600 of its intelligence officers in Europe with diplomatic cover were expelled.

Britain used a similar tactic when James Cleverly, the Home Secretary, expelled Col Maxim Elovik, Moscow’s defence attache, after the allegedly Russia-linked arson attack on the east London warehouse that was being used by a business providing aid to Ukraine.

Four men will go on trial next year accused of setting fire to the commercial property, a court heard last month.

Lack of sophistication 

Alexander Lord, lead Europe-Eurasia analyst at Sibylline, a geopolitical risk firm, said: “The capabilities these gangs can provide are pretty low-level, but they can still achieve Russian foreign policy objectives, namely, destabilising the West, deterring European decision-makers against supporting Ukraine and exacerbating polarisation and societal tensions across not only Nato but the European Union.” 

The lack of sophistication is a particular worry for Western intelligence services, with the proxies now relied on by the Kremlin more likely to cause collateral damage because of their lack of skills with explosives.

A Western counter-intelligence officer told the Financial Times: “There is a greater chance of collateral damage and casualties as the proxies are not skilled in tradecraft, such as explosives.” 

Their theory was displayed earlier this week when the former Russian soldier, from Ukraine’s eastern Donbas region, was badly burned in an explosion on Tuesday in a hotel room in Roissy-en-France, near Paris’s Charles de Gaulle airport.

Investigators confirmed they had discovered bomb-making materials, as Volodymyr Zelensky, the Ukrainian president, arrived in France to join commemorations marking the 80th anniversary of D-Day.