Fears are growing of a multiple-casualty event resulting from Russia’s increasingly reckless sabotage attacks across continental Europe and the UK.

Experts and officials are concerned that Russia’s escalating campaign of hybrid warfare against Europe could result in a miscalculation that results in unintended civilian casualties.

One diplomat from a country on Nato’s eastern flank summed up Russia’s approach as “how many things can we do without getting busted?”

European governments are understood to be quietly preparing for the growing possibility of a destabilising attack on Europe that causes fatalities while remaining below the threshold of open war.

Estonia’s foreign minister, Margus Tsahkna, said on Thursday that Russia was waging “full-scale terror” across Europe, in an attempt to spread fear and break Western support for Ukraine. “They are turning on the heat, trying to boil Europe as a frog over the years,” he said. “And then testing and dividing our unity.”

Talks between EU ambassadors in “restricted format” – without phones or assistants – have been ramping up since the discovery of an explosives-laden drone at Leipzig airport in Germany in August, reported this week. The latest talks focused on the rising risk of more serious attacks that could cause large-scale casualties.

One official told the news outlet: “Given the scope and scale of Russia’s action there are bound to be casualties sooner than later. It’s sheer luck there haven’t been any yet.”

The past few weeks have seen a sharp uptick in “grey-zone” warfare that several European governments have attributed to Russia, including arson attacks, drone airspace incursions and infrastructure sabotage.

“A high-impact attack is a plausible scenario within six months,” according to Annabelle Walker, a Europe analyst at the risk intelligence consultancy Sibylline, naming the Baltics, Germany and Poland as among possible targets. “The threat landscape has deteriorated pretty significantly in the last couple of months. This intensification seems to be reflecting a great tolerance for risk and collateral damage.”

Walker said an attack could involve a high-impact improvised explosive device going off in a civilian area or higher-impact arson that inflicts casualties, although intelligence services were likely to pick up anyone trying to make a bomb on such a scale. Alternatively, Russia could orchestrate a major cyber attack on critical national infrastructure, or use drones to disrupt major airports.

While Moscow might not intend a “mass-casualty operation”, she added: “The less risk-averse it becomes, the more likely we see something going wrong and then causing an unintended escalation.”

She said another possibility could be “potentially targeted assassinations against leading defence executives”. Walker emphasised that a single flashpoint incident was unlikely to be the main point of concern, with the likelihood of such an attack by Russia or a Russian-backed organisation fairly low in the coming year.

More targets than we can protect

Hybrid war, which blends conventional combat with cyber attacks and covert operations, nevertheless risks large-scale destruction and civilian casualties. Ten sailors are still missing after their ship was sunk by drones in Bulgaria’s Black Sea exclusive economic zone on Tuesday. It is not yet clear who was behind it, but if it turns out to be Moscow, it would mark a huge escalation of Russian aggression against Nato.

Russia’s GRU military intelligence is believed to have organised the recent failed plot to hit a plane at Leipzig airport, according to a report. Likewise, Western intelligence believes the GRU was behind a 2024 explosives plot targeting the UK, Germany and Poland. In July, a Russian cruise missile crashed into Polish territory. Drones flying near airports, including in Denmark and Norway, have prompted regular airspace closures since last year.

The i Paper understands that officials think that explicitly linking incidents of terrorism and sabotage to Moscow – where a connection can be proven – is vital for neutralising Vladimir Putin’s attempts to sow division in European societies and undermine support for Ukraine.

“A key part of the challenge is that the range of potential targets is so wide: from power plants to airports to subsea cables to factories and much else – anything can be targeted,” Katja Bego, senior research fellow in Chatham House’s Europe programme, told The i Paper. “There are more potential targets Russia could try to aim for, than European countries can meaningfully protect.”

‘Threat to UK bases is systemic’

Targets in Britain are broadly still largely defence-adjacent sites and assets that support Ukraine. A suspected plot at RAF Fairford in Gloucestershire is under investigation, while last year six men were jailed for a Russia-linked arson attack on a London warehouse providing aid to Ukraine.

The Metropolitan Police on Thursday said it had arrested two Latvian men on suspicion of trespass offences at RAF Molesworth in Cambridgeshire. Meanwhile, a Royal Navy serviceman has been charged with spying for Russia.

“RAF Fairford once again highlighted that a lot of military infrastructure is also at risk,” said Bego. “Especially during a time of far easier access to drones, better protecting military bases that are often quite open and lightly protected should be an immediate priority.”

That threat came after pro-Palestine activists broke into RAF Brize Norton in Oxfordshire last summer, highlighting security lapses at UK bases.

On Sunday, America withdrew its B-1 bombers from Fairford after US officials said they had intelligence that Iran was plotting a drone attack against the base.

There is growing concern that a hostile state could use drones to attack a UK military base, especially since Ukraine’s Operation Spiderweb in June 2025, when drones smuggled into Russia in lorries were released en masse to attack airbases, resulting in huge losses to Moscow’s bomber fleet.

The i Paper understands that there is no clear British policy on shooting down drones. Responsibility for doing so, and understanding of when a drone is considered to pose an active threat, is currently in flux.

Recent Iranian drone attacks on US bases in the Middle East, which damaged American planes and killed personnel, exposed the vulnerability of bases without hardened shelters (like some of those in the UK) to swarms of cheap drones.

“It’s all bases,” he told The i Paper. But while a base such as RAF Coningsby could bring fighter aircraft into hardened shelters, he said this was not possible at other locations for bigger transport planes or air-to-air refuelling tankers.

“It is physically not possible to protect these aircraft by putting them into a shelter because there are not enough shelters…” he said. “So I think those bases, as well as civilian airports – this is not just a military issue, it’s a civilian issue – are vulnerable.”

“A significant number of UK bases are in need of increased investment in hardened facilities, greater situational awareness and counter-UAS [drone] cover to name just a few line items,” said William Freer, research fellow in national security at the Council on Geostrategy. “For over three decades the UK has had a penny-wise but pound-foolish approach to rear area security – saving a few tens of million pounds on additional protection puts at risk billions of pounds of assets.”

When it comes to deterring Russia, the UK and Nato allies have been accused of falling short. Nato has been approached for comment.

‘All of Europe is in the firing line’

While attacks on the UK have been lower-level than elsewhere, Russia is showing intent to expand their scale, Caspar von der Schulenburg, Europe analyst at Sibylline, told the What Just Happened? podcast. “We are already seeing a sustained kinetic campaign or a transition to kinetic incidents [in Europe], whereas in the UK for now it appears that preparation and reconnaissance and more low-level attacks are still predominant. But we can already see that there is an increased intent.”

In recent months, the UK government agreed to send Storm Shadow cruise missile blueprints to Ukraine, while Kyiv granted Britain access to its Avengers AI warfare training lab. Moscow, hellbent on deterring Europe from supporting Ukraine, said this would “add fuel to the fire” of the war. Tobias Ellwood, a former defence minister, said Britain “should brace for grey-zone retaliation. And for this we are woefully unprepared”.

Countries like Poland and Germany are seeing increasing attacks on energy, telecommunications, factories and logistics. Britain, as an island, is highly vulnerable to Russian sabotage of critical undersea cables that carry energy and data. Its factories producing drones for Ukraine will also be major targets.

“All European countries are in the firing line,” said Bego. “If anything, it is those countries furthest from the border with Russia that form the softest targets, as they are often least psychologically and practically prepared for this threat.”