Estonian naval ships are taking part in stepped-up patrols in the Baltic Sea by NATO countries after undersea power and communications cables have been damaged in recent months.

Officials say the damage to Estlink 2, a power connection with the capacity to provide half of Estonia's winter electricity needs, did not disrupt service, although it did drive up energy prices in the country and the other Baltic nations.

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.