An initial investigation into possible sabotage has been launched by four NATO countries -- Finland, Germany, Sweden and Lithuania -- after two underwater telecommunications cables across the Baltic Sea were cut in two separate incidents in recent days, a European official told ABC News.
Sweden is leading the investigation, as both incidents occurred in the Swedish economic zone, a Swedish Ministry of Defense official told ABC News.
"Against the backdrop of the security situation, the government is following developments very closely and is in close contact with its authorities. It is central that greater clarity is brought to the cause of this event," Swedish Minister for Civil Defense Carl-Oskar Bohlin told ABC News in a written statement.
An underwater cable that runs between Lithuania and Sweden in the Baltic Sea was cut on Sunday around 10 a.m. local time, Telia spokesperson Audrius Stasiulaitis told ABC News. Telia is a Lithuanian telecommunications company. A cable that runs between Germany and Finland was cut on Monday around 3 p.m. local time.
"Our monitoring systems could tell there was a cut due to the traffic disruption and that the cause was not the equipment failure but physical damage to the fiber cable itself," Stasiulaitis said.
Internet traffic was not impacted, as the company rerouted the traffic after the disruption occurred, Stasiulaitis said.
The underwater cable has been in place since 1997, Arelion spokesperson Martin Sjogren told ABC News. Arelion is a Swedish telecommunications company that operates and owns the cable.
Arelion is in touch with Swedish authorities about the incident, Sjogren said.
A repair ship will need to get on-site in order to determine the cause of the break, Sjogren said. Repair work is scheduled to start later this week and could be finished by late next week depending on the weather, Sjogren added.
The Lithuanian Prosecutor's Office has opened an investigation into the matter, a statement from their office said Tuesday. Swedish police have also opened a preliminary investigation into the matter, a statement from Swedish police said Tuesday.
The foreign ministries of Germany and Finland said in a joint statement on Monday they were "deeply concerned" by the severing of an undersea cable connecting the two countries across the Baltic Sea -- one of two Baltic Sea connections suddenly damaged in recent days.
Finnish company Cinia reported a "fault situation" with its C-Lion-1 submarine cable on Monday afternoon, saying in a statement that an investigation and repair work were underway.
Cinia did not offer any explanation for the interruption to the connection and said undersea cable repairs generally take between five and 15 days. The 730-mile cable has connected Finland to central European communication networks since 2016.
The German Interior Ministry confirmed to ABC News that authorities believe the cable was severed by an external force near the Swedish island of Oland.
Berlin and Helsinki said they were "deeply concerned about the severed undersea cable."
"The fact that such an incident immediately raises suspicions of intentional damage speaks volumes about the volatility of our times," the joint foreign ministries' statement continued.
"A thorough investigation is underway. Our European security is not only under threat from Russia's war of aggression against Ukraine, but also from hybrid warfare by malicious actors. Safeguarding our shared critical infrastructure is vital to our security and the resilience of our societies."
The damage to the C-Lion-1 cable came one day after Telia Lietuva -- a Swedish telecoms company in Lithuania -- said one of its undersea telecommunications cables linking Lithuania and Sweden across the Baltic Sea sustained damage.
That cable -- which intersects with the C-Lion-1 Finnish-German cable -- was damaged on Sunday morning, company spokesperson Andrius Semeskevicius told local media.
The damaged cable has been the subject of faults and accidents in the past. But, Semeskevicius told Lithuanian National Radio and Television, "since both are damaged, it is clear that this was not an accidental dropping of one of the ship's anchors, but something more serious could be going on."
The cause of the damage to the cables has yet to be established. The interruptions come against a backdrop of concerns over Russian sabotage operations in Europe and elsewhere, prompted by Western support for Ukraine in its defensive war against Moscow.
The Baltic Sea has been the scene of mysterious undersea incidents in recent years, such as the sabotage attacks on the Nord Stream 1 and 2 natural gas pipelines running from Russia to Germany in 2022.
The following year, a Chinese container ship -- the Newnew Polar Bear -- dragged its anchor for more than 100 nautical miles through the Gulf of Finland, damaging an undersea natural gas pipeline and two telecommunications cables. Finnish and Estonian authorities are conducting a joint criminal investigation into the incident.
ABC News' Aicha El Hammar and Ellie Kaufman contributed to this report.