NATO's standing maritime group is to set off from its base in the German port of Kiel for the Baltic Sea to monitor critical underwater infrastructure following several suspected acts of sabotage, the group's commander said on Friday.

NATO is increasing its surveillance operations in the Baltic Sea region with two ships deployed to the area following suspected sabotage of undersea cables between Finland and Estonia.

Finnish police said on Tuesday they had recovered a lost anchor from the seabed as part of an investigation of suspected sabotage against power and internet cables in the Baltic Sea.

General Mark Rutte says the military alliance will step up patrols in the Baltic Sea area as Finnish investigators work to establish whether a ship linked to Russia sabotaged undersea cables there this week.

If the Russians see that we are present there, the likelihood of such sabotage acts immediately decreases," said one navy commander.

Incidents of suspected sabotage of undersea cables and pipelines are prompting countries to step up security measures. Estonia's navy has launched an operation to try to counter sabotage, after cables were damaged in December.