The suspected sabotage of two telecommunications masts – key parts of Sweden’s infrastructure – has reignited fears of foreign spies and the readiness of depleted security services in a country on the frontline of growing tensions with Russia.

A 300-metre-high mast in south-western Sweden collapsed on Sunday in what police say was sabotage. Police suspect either a prankster, local extremists or international saboteurs and have contacted the country’s spy service to investigate.

“We are 100% certain the tower has been sabotaged,” police head investigator Jan Johansson told the Aftonbladet newspaper. “It could be something international, that they want to test what happens when taking out a mast like this.”

The state-owned Teracom telecommunications company has upped security and surveillance after Sunday’s incident.

In early May, a cable to another mast in the same region, dedicated to rescue services communications, was cut off. On Tuesday, the bomb squad was called to investigate a suspicious package near another mast in central Sweden, police told local media, but the package turned out to be harmless.

Police confirmed to Reuters that there were two suspected incidents of sabotage on 4 May and on Sunday but did not confirm possible international links.

However, regardless of who ultimately proves to be responsible for the incidents, for most Swedes, any official pointing the finger at international sabotage immediately signals Russia amid a return to the kind of cold war paranoia that once permeated the Nordic region.

“I would guess there is an international link,” analyst Hans Brun of the Swedish National Defence college told Swedish radio. “To be really honest it’s just a judgment and isn’t based on research, but in that case it is only Russia you can think would be interested.“

Sweden has for years seen Russia as its biggest geopolitical threat and in April Russia’s foreign ministry warned of consequences if Sweden joined Nato. In reporting the sabotage, Dagens Nyheter, one of Sweden’s biggest-selling newspapers, underscored how security services warned this year of Russian agents spying on important infrastructure.

Since the Ukraine crisis, Sweden has seen increasing tensions with Russia, heightened by Russian warplanes crossing its borders as well as a hunt for a suspected Russian submarine off Stockholm in 2014. In March, cyber-attacks on major Swedish newspapers also brought fears of Russian meddling.

Reuters contacted the Russian foreign ministry for a comment. There was no immediate reply.

The Svenska Dagbladet newspaper said the collapse of the mast left some 85,000 households without TV broadcasts. The masts are also used by the police and military as well as transmissions of public emergency announcements.

“The sabotage puts a finger on a sore spot in Swedish defence when the armed forces have chronic manpower problems and the police are busy checking passports at the Oresund Bridge?” commentator Linda Nordlund wrote in the newspaper, referring to the introduction of border controls with Denmark to deal with an influx of asylum seekers.

