Western Europe must brace itself for an escalation in Vladimir Putin’s hybrid war, including “state-sponsored terrorism and sabotage”, diplomats of nations bordering Russia have warned.

The i Paper spoke to multiple officials from countries on Nato’s eastern flank to hear their assessment of the current threat posed by Putin, as Poland described a fire at a Starlink centre in the country that provides internet connection to the Ukrainian army as “a deliberate act of sabotage”.

While the diplomats do not believe Putin is likely to invade a Nato country – a move that could spark a full-blown war involving the UK – there is profound concern about Russia escalating its “hybrid” operations.

Such non-conventional forms of attack could see “state-sponsored terrorism, state-sponsored murders, sabotage” being waged across the continent, one senior diplomat warned.

‘They are always testing us’

The discovery of an explosive-laden drone at Leipzig airport in east Germany last month is seen as heralding a new recklessness from the Russian leader.

The senior diplomat said that it showed the Kremlin is “increasing the intensity or riskiness” of its operations.

“They are always testing us,” said one diplomat from a Baltic country. “They want to know how far they can go, how far they can provoke us, before we respond.”

Another diplomat warned of the risk of “state-sponsored terrorism, state-sponsored murders, sabotage… something which is not military but can be very bad. Derailing a train. Blowing up something…”

Several officials from eastern flank countries summed up Russia’s approach by quoting the infamous maxim attributed to Vladimir Lenin: “Probe with bayonets. If you encounter mush, proceed; if you encounter steel, withdraw.”

Putin and those around him are both highly opportunistic and constantly probing for weaknesses when it comes to Nato’s defences and the solidarity of the alliance’s Article 5 commitment to treat an attack on one as an attack on all, the diplomats say.

There have already been politically motivated killings or attempted murders on British soil thought to be orchestrated by the Kremlin. These include the murder of Alexander Litvinenko in 2006 by polonium poisoning, and the attempted murder of Sergei and Yulia Skripal in 2018 with the Novichok nerve agent, which killed British citizen Dawn Sturgess.

An arson attack on property linked to Sir Keir Starmer in May 2025 was linked to Russia.

And last autumn, six men were jailed for their parts in a Russian-commissioned arson attack on a London warehouse providing aid to Ukraine.

On Thursday, it was reported in the Spanish press that Russia is planning to launch seaborne drone attacks against Italy, Spain and France.

What else is fueling the concerns?

Security analysts think that Putin is becoming increasingly desperate, as the war in Ukraine threatens his popularity and the Russian economy – long-range strikes by Ukraine have caused significant damage to Russia’s oil industry, causing fuel shortages.

Some experts believe he may try to provoke a crisis elsewhere in Europe to try to achieve a resolution in Ukraine on Russia’s terms.

There are several issues compounding the worries about hybrid operations.

The first, paradoxically, relates to Russia’s dearth of professional agents in Europe. In recent years, many European countries, including the UK, have expelled Russian diplomats accused of being spies.

It has meant that Russian intelligence agencies increasingly use low-level, untrained individuals who are happy to commit criminal acts on an ad hoc basis for money.

One diplomat The i Paper spoke to warned of the risk that such amateurs – sometimes dubbed “disposable assets” – could go over the line and commit acts of violence which are more aggressive or harmful than intended by their handlers.

The second worry relates to the nature of Europe’s response to hybrid attacks to date. After the Leipzig incident, Germany attributed the attack to Moscow and responded by shuttering the Russian consulate in Bonn and a Russian cultural centre in Germany.

The Kremlin retaliated by closing German cultural centres in Russia.

Several of the European officials The i Paper spoke to said that Berlin’s response would be viewed as pusillanimous by Moscow and would be unlikely to temper future malign activities.

The senior diplomat said: “[Russia] do what they can in Germany. Germany’s response gets a mirrored response from Russia. So what’s the total? Russia 1, Germany 0.”

They suggested that a more fitting response would have been to immediately send Kyiv 20 Taurus missiles – a German cruise missile which Berlin has so far refused to give to Ukraine – with a warning that if there were further attacks they would send 50 more.

“We should be doing what we need to do in order to support Ukraine and constrain Russia, and if Russia does something then we should have a proper response,” they said.

Another official agreed that Berlin’s response was weak and suggested that a total ban on German visas for Russian citizens would have been more appropriate.

Large-scale attack unlikely

The Nato countries which share borders with Russia – Norway, Finland, Estonia, Latvia, Lithuania and Poland – are clear-eyed about the threat posed by Moscow.

They do not think that a large-scale attack is likely in the short term.

One senior diplomat characterised talk of an invasion as “hysteria” from “armchair” experts. “We don’t see it,” they said. “We see very well what is happening in Russia.”

Several officials told The i Paper that there is currently “lots of emptiness” on the Russian side of the border with Nato, precisely because Moscow has been forced to divert so many troops to Ukraine.

Nato has nine multinational battlegroups in member countries along the eastern flank (in Estonia, the battlegroup is led by Britain). Estonia, Latvia and Lithuania are working on a ‘Baltic Defence Line’ of bunkers, anti-tank ditches and obstacles, as well as spending heavily on artillery, ammunition, air defence and counter-drone systems.

In the case of an attack in the Baltic, Finland and Estonia possess sophisticated surface weapons systems which would enable them to close the Gulf of Finland – a crucial shipping route for Russian oil and imports from the West.

At the same time, the fight could be taken to Russia using long-range missile strikes on targets such as St Petersburg and Ust-Luga, a major export terminal.

The senior diplomat said: “What they (Russia) can do with very limited early warning would be insignificant, and we would deal with that.

“If they aim to do something which would be significant militarily, then that would take many months of preparation, and it’s not just us who will be picking it up.

“It’s not going to be something coming out of the blue.”