Dual telecommunication cable faults
On 17–18 November 2024, two submarine telecommunication cables, the BCS East-West Interlink and C-Lion1 fibre-optic cables were disrupted in the Baltic Sea. The incidents involving both cables occurred in close proximity of each other and near-simultaneously which prompted accusations from European government officials and NATO member states of hybrid warfare and sabotage as the cause of the damage. Currently, the damage to those undersea cables has not been conclusively attributed to any specific party. Investigations are ongoing and since 19 November, the Chinese cargo ship is under scrutiny due to its presence near the cables at the time of the incidents. Western intelligence officials believe the ship's anchor may have caused the damage, either accidentally or under the influence of Russian intelligence.
Background.
The BCS East West Interlink is a long submarine data communication cable that runs through the Baltic Sea, built in 1997 by Alcatel and owned by Arelion. It connects Sventoji in Lithuania to Katthammarsvik on the east coast of the Swedish island of Gotland. From Gotland another cable passes data to the Swedish mainland. The C-Lion1 is a submarine communications cable between Finland and Germany. The cable is owned and operated by Finnish telecommunications and IT services company Cinia Oy; it is the first direct communications cable between Finland and Central Europe following, and has operated since May 2016.
A year before, a similar undersea infrastructure disruption event, the Balticconnector incident, occurred when the Chinese ship "Newnew Polar Bear" dragged its anchor across the seabed, damaging a pipeline and submarine cables between Sweden and Estonia.
Worldwide, about 200 undersea cables have been cut or disrupted annually as of 2024, due most frequently to unintentional damage from fishing equipment or the anchors of ships.
Disruption, 18–28 November 2024.
On Monday, 18 November 2024, the telecommunications company Telia Lithuania announced that the BCS East-West Interlink submarine cable between Lithuania and Sweden had been "cut" on Sunday morning at around 10 a.m. local time. At around the same time, the submarine cable C-Lion1 for data communication between Finland and Germany was cut in the same region of the Baltic Sea. As a result, both of their telecom services were disrupted. The C-Lion1 fault was discovered off the coast of the Swedish island of Öland. The two faults were detected about apart from each other. The BCS East-West cable is at a depth of and C-Lion at deep.
An Arelion spokesperson described the damage to the BCS East-West Interlink cable as "...not a partial damage. It's full damage." At the time of the incident, the cable provided about 1/3rd of the internet capacity of Lithuania.
According to C-Lion1 operator Cinia Oy, the cable was severed by an outside force. Cinia chief executive Ari-Jussi Knaapila stated that the company was in the process of conducting physical inspections at the site of the fault.
BCS East-West Interlink and C-Lion1 were restored on 28 November 2024.
Reactions.
On 18 November, the Foreign Ministers of Germany and Finland issued a joint statement expressing "deep concern" over the C-Lion1 cable's disruption, and expressed suspicion over possible hybrid warfare conducted by Russia, causing the disruptions in the midst of the Russian invasion of Ukraine and elevated tension against NATO member states. German Federal Defense Minister Boris Pistorius called the incident an act of sabotage. He further stated that "no one" believed that the cables were cut accidentally. The Lithuanian Naval Force announced increased surveillance of its waters in response to the damage and would discuss further measures with Lithuania its allies. The Lithuanian Armed Forces stated that NATO members corresponded with one another to determine the cause of the disruptions. 
European governments accused Russia of escalating hybrid attacks on Ukraine's Western allies, but not directly accusing Russia of destroying the seacables.
Kremlin spokesman Dmitry Peskov rejected suspicions and called it "absurd", accusing Russia without evidence.
On 26 November 2024, Chinese Foreign Affairs Ministry issued a statement of "no knowledge" regarding the incident.
Suspicious ships.
The Chinese cargo ship "Yi Peng 3" left the Russian Baltic Sea harbour Ust-Luga on 15 November 2024. Information about the destination of the ship offered by media outlets varied, the most frequently mentioned being Port Said, Egypt, while the analysis provider "MarineTraffic", said the destination was unknown upon departure. On 17 November, between 1:30 a.m. (UTC) and 11:19 a.m. the ship passed the Swedish island of Gotland. "Yi Peng 3" crossed BCS East-West. At around 10 a.m., the Lithuanian telecom provider Telia in Vilnius received a fault report: the connection between Šventoji, Lithuania, and Gotland, Sweden had been severed. The ship crossed several times over the position of damage of the two cables. "Yi Peng 3" continued its journey south. After Gotland, the freighter switched off its automatic identification system (AIS) signal for 7.5 hours. At 22:41 UTC the ship switched AIS back on and was located south of the Swedish island of Öland.
Three hours later, at 2 a.m. (UTC) on 18 November, the Finnish network provider Cinia reported a loss of data traffic via C-Lion1. It became clear that the cable between Gotland and Öland was damaged. In this area "Yi Peng 3" was traveling without an AIS signal. The Danish public broadcaster DR sent a drone to survey the ship, showing images of how one of "Yi Peng 3"'s anchors had become mangled – according to NZZ an indication that the freighter could have destroyed the cables.
On 19 November 2024 the Royal Danish Navy observed "Yi Peng 3" in the Baltic Sea after it was suspected to be involved in the sabotage. The detention of the Chinese vessel was the first enforcement action under the Convention for the Protection of Submarine Telegraph Cables since the Transatlantic cables incident of 1959. 
Since 20 November 2024, "Yi Peng 3" has been stationed at a sea position in the Kattegat off anchor and has been guarded by the Royal Danish Navy.
On 22 November, the German Coast Guard sent and the Swedish Coast Guard also sent "Poseidon", one of its largest ships, joining the Danish patrol vessel in monitoring "Yi Peng 3" in Kattegat.
On 22 November, a ship from the Finnish Coast Guard, the , a Swedish Coast Guard vessel and from the German Federal Police arrived at the damaged site of the C-Lion1 undersea data cable to examine it using remotely operated vehicles from the Swedish military.
On 17 December 2024 the Russian Navy sea rescue tug "Yevgeniy Churov" was reported to have approached the anchored "Yi Peng 3", passing it at very low speed and with its own AIS transmitter turned off.
On 18 December 2024 Chinese authorities allowed German and Swedish investigators to board "Yi Peng 3", but the mission was postponed due to bad weather. Finally, on 19 December, 14 Chinese, 9 Germans, 6 Swedes, 3 investigators from Finland and one Dane boarded the vessel in the Kattegat. The Chinese investigation team, accompanied by the Western observers, questioned the crew, inspected relevant pieces of equipment and reviewed documents. The Swedish Police and Swedish Accident Investigation Authority participated, conducting interviews with crew members and technical examinations, including of the anchoring equipment. Jonas Bäckstrand, Deputy Director General of the Swedish Accident Investigation Authority, noted that significant observations were made, though details remain undisclosed. The operation lasted for 5 hours.
The Chinese representatives did not permit access for Henrik Söderman, the Swedish public prosecutor, according to authorities of Sweden. The Swedish government had put pressure on Chinese authorities for the ship to move from international waters into Swedish territory to allow a full investigation.
On 21 December 2024 Danish authorities reported "Yi Peng 3" had weighed anchor and continued its voyage. A Swedish Coastguard statement said "Yi Peng 3" did so on its own initiative, with the given destination being Port Said in Egypt.
Investigations.
The Swedish Prosecution Authority opened an investigation into "sabotage" regarding the disruptions of both cables. According to the Swedish Navy, it had an "almost 100% identification" of the ships that were in the area of the two cable breaks. The navy is using a remote-controlled submarines to investigate the southern site of the two cables to support the Swedish prosecutor and police with their investigations.
Lithuania's Prosecutor General's Office launched a pre-trial investigation into terrorism. 
On 20 November, "Keskusrikospoliisi" (KRP), Finland's national bureau of investigation opened a criminal investigation into the rupture of the C-Lion1 cable on suspicion of "aggravated criminal mischief and aggravated interference with communications." On 26 November, the three nations signed an agreement to proceed with a joint investigation, coordinated through the Eurojust.
Following the allegations of sabotage by "Yi Peng 3", Sweden asked China to cooperate with the Swedish authorities on the case, according to Prime Minister Ulf Kristersson who emphasized that there was no "accusation" of any sort. Under the flag state principle, China has jurisdiction over "Yi Peng 3" and ultimately determines any necessary investigations or prosecutions. Despite the presence of Danish, Swedish, and German patrols observing the vessel since 19 November, maritime law requires China's consent for any significant legal actions to be taken. China agreed on 29 November 2024 to cooperate in the investigation. China was ready to "work with relevant countries to find out the truth," said Mao Ning, the Foreign Ministry spokeswoman, China and Sweden in close contact on the matter, she added. On 19 December, representatives from Sweden, Germany, Finland, and Denmark were invited by Chinese authorities to board the vessel as observers during a Chinese-led investigation. While Swedish prosecutors leading a separate European investigation were not permitted to board, Sweden’s accident investigation authority were invited to board. Jonas Backstrand, chair of Sweden's accident investigation authority, stated: "We are content with the visit onboard, which was relatively open and transparent, and we had the possibility to see what we wanted to see and to talk to the crew members that we wanted to talk with."
European authorities have not ruled out sabotage while U.S. intelligence officials assessed that "the cables were not cut deliberately".