Russia is using a network of holiday homes in the Baltic region as “Trojan horses” to wage hybrid war on the West, a Telegraph investigation can reveal.

Western officials are taking action against hundreds of Russian-linked homes in Lithuania, Sweden and Norway, which have been bought close to strategic military sites or key infrastructure.

The most serious case is in Sweden, where a Russian oligarch-linked property has been designated a “critical threat” because it sits at the entrance to the southern Muskö naval base.

Other holiday homes have been purchased by Russians near the Nato air bases of Šiauliai Zokniai and Panevėžys Pajuostis in Lithuania. In Norway, cabins linked to Kremlin-connected figures overlook the Bardufoss air base, one of the country’s most important military bases, which hosts F-35s.

Western officials are concerned that the properties could be used to launch drone attacks on nearby bases or as a staging area for sabotage attacks against the Nato allies.

Such attacks form part of Moscow’s ever-expanding hybrid war campaign, which has sought to sabotage factories in London and Warsaw, and assassinate defence executives who have provided military support to Ukraine.

The Telegraph has learnt that the seven-bedroom property near Sweden’s Muskö naval base is owned by Tatiana Sazonova, the wife of Stanislav Aleshchenko, a Russian oligarch and ally of Vladimir Putin.

Swedish property documents show that the property was bought for 18.6m Swedish kroner (£1.4m) on Aug 14 2017, years before Russia was considered a critical threat to Sweden.

Pål Jonson, the Swedish defence minister, told The Telegraph his government would seize the “strategically important property”, because it considered the owner a “security threat” to the Muskö facility.

He said: “It is the only site in the area that is not at the disposal of the Swedish armed forces, leaving a critical gap in the defence of the naval base. The property is currently owned by an individual holding Russian citizenship who is assessed to pose a security threat to the Swedish armed forces.”Construction work seems to be taking place at the site of the house in Muskö bought by Russians Mr Jonson said securing access to the property would be crucial to establishing a defence of the strategic naval base, particularly against the growing threat posed by drones.

Eitvydas Bajarūnas, Lithuania’s former ambassador to London, said: “In the Baltic states, there is concern that Russia could use property ownership or proxies as a kind of ‘Trojan horse’.

“Not necessarily for immediate military action, but for intelligence gathering, surveillance, influence or even preparation for sabotage.”

He added: “The purpose of these restrictions is preventive: to reduce vulnerabilities around military and strategic infrastructure before they can be exploited in a crisis.”A former security policy chief at the Lithuanian foreign ministry, Mr Bajarūnas also served as ambassador-at-large for hybrid threats, a role focused on Russian hybrid warfare, from 2016 to 2020.

An ally of Vladimir Putin owns a property near Sweden’s Muskö naval base When The Telegraph visited the property this month, it was boarded up and covered in scaffolding. Neighbours said the owners had put up the fences to keep people off the property, because onlookers kept trespassing.

The renovations to the house include the use of dynamite to create a basement beneath the property, according to Swedish military reports.

Neighbours said the building work had been going on for at least a year and a half, and that they had not seen the owner since before the 2022 Ukraine war, but that she seemed like “a nice girl”. Some neighbours told The Telegraph they were uncomfortable with the allegations surrounding the property Ms Sazonova previously denied knowing that the property was near a military base when she was questioned by Swedish news outlet Bulletin. The Telegraph made several attempts to reach her for comment but did not receive a response.

The house in Muskö is covered in scaffolding, and renovations have been going on there for months Sweden’s armed forces have publicly warned that the property is owned by individuals who present a “security threat” to their troops, without identifying them by name.

The Telegraph has independently geolocated the property, which sits on the southwestern tip of Muskö island and is just a stone’s throw from the naval base. The base is understood to contain three docks that were built to host destroyers and submarines.

According to an estate agency listing, which remains online but marks the home as sold, the property has seven bedrooms, three bathrooms, a pebble beach and a motorboat jetty.

The disclosure will raise concerns that Russia’s wider web of properties in Europe could be used to launch drone attacks on nearby military infrastructure.

In Lithuania, the government has passed new reforms to ban Russian ownership of properties near sensitive sites to avoid them being used for nefarious purposes.

Frank-Walter Steinmeier, the Swedish president, and his wife Elke Budenbender take a Swedish navy combat boat to the Berga naval base during a visit to Musko in May Lithuanian officials have warned that Russia-linked individuals have bought property near Šiauliai Zokniai air base, the Panevėžys Pajuostis air base, the Gaižiūnai military training area in Rukla, and Vilnius and Palanga airports, as well as other locations.

Šiauliai air base is key for Lithuania because it is the centre of operations for Nato’s air policing mission, which hosts fighter jets that patrol along the alliance’s eastern flank. It is also the main air base of the Lithuanian air force, the Kop.

Panevėžys Pajuostis is not currently operational but was a strategically important base during the Cold War, when it hosted heavy transport aircraft under Soviet rule.

Mindaugas Lingė, a senior MP for the centre-Right Homeland Union party, said: “We have already seen property acquired by Russian-linked owners used for provocations and covert operations elsewhere in Western Europe.

“It would be naive to assume the same is not being attempted in Lithuania, a front-line Nato state bordering both Russia and Belarus.

“For national security, what matters is not why someone bought a property, but what it could be used for. A property next to a military base or other strategic site can serve as an observation post, a place to store equipment, or a launch point for drones and sabotage.”In Norway, several cabins in Målselv Fjellandsby, a winter sports resort near Norway’s northern Bardufoss military base, have had Russian owners since 2010, according to Norwegian broadcaster TV2.

Tobias Billström, Sweden’s former foreign minister and the director of Nordic Air Defence, said Russia had increased hostilities towards Sweden since it joined Nato.

He said: “We strongly support Ukraine and joined Nato, two things which made Moscow openly declare that we are a country hostile to Russian interests.

“We are seeing an increasing amount of intent to disrupt Sweden and the Baltic countries, and advance Russian intelligence interests. What we are talking about in Muskö, a property procured and disguised as something else – that’s an old Russian strategy.”Swedish officials are already locked in a legal battle to expropriate a Russian Orthodox church in Västerås, central Sweden, which sits across the road from a strategically important airport.

The Telegraph visited the church earlier this year but no one was available for comment on the allegation made by the Swedish intelligence services that it was being used to spy on the nearby airport.

As The Telegraph revealed earlier this year, Russian officials have been trying to manipulate Swedish churches into letting them rent office space near critical infrastructure.

Kristina Smith, the head of the Church of Sweden’s crisis-planning unit, said at the time: “We have given a general warning against letting the Russian Orthodox Church rent or borrow church facilities, because we noted the places they wanted to borrow were next to military installations.”Moscow has even resorted to using so-called spy nuns as a means of spreading pro-Kremlin propaganda in Sweden and other Nato allies.

Last year, Belarusian nuns from St Elisabeth Convent were allowed to sell trinkets to Swedish churchgoers as part of an outreach programme to Christians living in dictatorships.

The church that hosted the nuns in Täby was unaware that the convent supported the invasion of Ukraine and that it had links to the GRU, Russia’s military intelligence unit.

The nuns are so fond of Putin’s war that they have been nicknamed the “Z-Nuns”, owing to their penchant for posing with the “Z” symbol of Russia’s invasion of Ukraine.

St Elisabeth nuns have also been photographed in parts of eastern occupied Ukraine wearing flak jackets, where they work to improve the morale of Russian soldiers.

The Swedish government has already moved to pass new laws to give the state “stronger powers to intervene against existing property holdings when they pose a risk to Sweden’s security”, Mr Jonson said.

Laws blocking Russians or Russia-linked figures from buying up new properties for the same purpose have already come into force.

Mr Jonson said: “New legislation that entered into force on 1 July strengthens security screening when property connected to security-sensitive activities is transferred and allows authorities to prevent unsuitable transfers.”

He added: “The Government is also working with proposals for strengthened control of certain foreign acquisitions of Swedish real estate. The purpose is to give the state greater ability to scrutinise and, where necessary, prevent foreign acquisitions that could harm essential total-defence interests.”