UPDATE 2-Estonia's navy to protect Baltic Sea power link after cable damage

Adds background on damaged cables in paragraphs 2 and 5-7, detail from public broadcaster in paragraph 8

STOCKHOLM, Dec 27 (Reuters) - Estonia's armed forces have launched a naval operation to protect the Estlink 1 undersea power cable in the Baltic Sea in response to the damage this week of a parallel electricity line, Foreign Minister Margus Tsahkna said on Friday.

Finland on Thursday seized a ship carrying Russian oil on suspicion the vessel caused an outage of the Estlink 2 undersea power cable which, like Estlink 1, connects Finland and Estonia, and that it also damaged four internet lines.

Baltic Sea nations are on high alert for acts of sabotage following a string of outages of power cables, telecom links and gas pipelines since Russia invaded Ukraine in 2022, although subsea equipment is also subject to technical malfunction and accidents.

Damage to subsea installations in the region has now become so frequent that it is difficult to believe this was caused merely by accident or poor seamanship, Tsahkna said on Thursday.

Finnish investigators believe the seized ship - the Cook Island-registered ship, named as the Eagle S - may have caused the damage by dragging its anchor along the seabed, one of several such incidents in recent years.

"If there is a threat to the critical undersea infrastructure in our region, there will also be a response," Tsahkna said on social media X.

The 658 megawatt (MW) Estlink 2 outage began at midday local time on Wednesday, leaving only the 358 MW Estlink 1 in operation between the two countries, operators Fingrid and Elering have said.

Estonian public broadcaster ERR reported on Friday that the Baltic country had despatched a patrol ship, the Raju, to the waters where the Estlink 1 runs, and that the country hoped NATO allies would also deploy ships.

(Reporting by Anna Ringstrom, editing by Terje Solsvik and Tomasz Janowski)

((anna.ringstrom@thomsonreuters.com;))