NATO is deploying eyes in the sky and on the Baltic Sea to protect cables and pipelines that stitch together the nine countries with shores on Baltic waters.

After a series of suspected undersea cable cuttings, NATO has launched a new surveillance and deterrence mission to protect critical infrastructure under the Baltic Sea.

Subsea cables are especially vulnerable to sabotage or even exploitation, as they are extremely long, difficult to monitor, and unprotected against a determined adversary. If nothing else, these events should alert governments and private-sector providers that the seabed is no longer insulated from malign actors.

The undersea cable is based in the Baltic Sea, and may have been deliberately damaged on Sunday, according to officials in Sweden.

Sweden has opened a preliminary investigation into suspected aggravated “sabotage” and ordered the detention of a vessel in the Baltic Sea suspected of damaging an underwater fiber optic cable connecting Latvia and the Swedish island of Gotland earlier that day.

The Nordic country has opened an investigation into the damage, just weeks after NATO stepped up its military presence in the area following a series of similar incidents.

A Bulgarian shipping company on Monday denied that one of its ships had intentionally damaged an underwater fiber optic cable connecting Latvia and the Swedish island of Gotland.