Tensions have mounted around the Baltic Sea since Russia's invasion of Ukraine in February 2022 and after Finland and Sweden joined NATO, with a string of incidents involving damage to undersea cables and other infrastructure.

In a report on Tuesday the Swedish Accident Investigation Authority (SHK) found that the Yi Peng 3 cut the two telecommunications cables after dragging its anchor off Sweden's southeastern coast for one and a half days and 180 nautical miles.

But it said it was unable to conclude definitively that the vessel, built in 2001 and owned by Chinese company Ningbo Yipeng Shipping Co, cut the cables on purpose.

"There are two alternative scenarios for the incident, one of which is that the ship deliberately dropped anchor to cause damage to seabed infrastructure," the authority said.

"Arguing against this alternative is the deliberate risk to the ship entailed in releasing the anchor at speed, with high risk that the ship and crew operating the anchor would be seriously harmed during the release," it said.

"The other alternative is that the anchor came loose because it was poorly or not at all secured," the SHK said.

However the lack of damage to the ship and the length of time the anchor spent on the sea floor "speak to some extent against this scenario", it added.

On November 17, the Arelion telecommunications cable running from the Swedish island of Gotland to Lithuania was damaged.

The next day, the C-Lion 1 communications cable linking Finland to Germany was cut south of Sweden's Oland island.

The SHK noted that it was only allowed on board to examine the Yi Peng 3's anchor and question crew members more than a month after the incident, and was not granted access to any electronic data.

Many experts and political leaders have attributed a spate of incidents in the Baltic since Moscow's invasion of Ukraine to a "hybrid war" carried out by Russia.

Sweden, Finland and Germany all launched investigations over the November 17-18 incidents and Swedish police said they suspected "sabotage".

The SHK said its assessment "does not prevent the Swedish Prosecution Authority from conducting a preliminary investigation into a suspected crime".