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

Shipping firms may need to pay a fee to use the Baltic Sea, one of the world's busiest shipping routes, in order to cover the high costs of protecting undersea cables, Estonia's defence minister said on Wednesday following a spate of breaches.

An undersea data cable between Latvia and Sweden was damaged early on January 26, the latest in a series of similar incidents in the Baltic Sea in which critical seabed energy and communications lines are believed to have been severed by ships traveling to or from Russian ports.

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.

Estonia's defence minister on Wednesday said ships may have to pay a fee to use the Baltic Sea to cover costs of protecting undersea cables.

STOCKHOLM (Reuters) - Swedish authorities boarded a Maltese-flagged ship seized in connection with the latest breach of cables running along the bottom of the Baltic Sea to begin an investigation into the matter, the country's security police said on Monday.

Swedish authorities have seized a ship suspected of damaging a data cable running under the Baltic Sea to Latvia. The Vezhen - a Maltese-flagged ship - is now anchored outside the Swedish port of Karlskrona.

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.

Shipping firms may need to pay a fee to use the Baltic Sea, one of the world's busiest shipping routes, in order to cover the high costs of protecting undersea cables, Estonia's defence minister said on Wednesday following a spate of breaches.

In addition to the patrols, Defence Minister Hanno Pevkur said countries are weighing other measures to protect cables, including installing sensors to detect anchors dragged across the sea floor or constructing casings or walls around the cables.

Several undersea cables running under the surface of the Baltic Sea have been damaged in suspected sabotage incidents in recent months.