Germany’s defense minister said damage to two fiber-optic cables on the sea floor appeared deliberate, but a culprit was not known.

Two undersea fibre-optic communications cables in the Baltic Sea, including one linking Finland and Germany, were severed, raising suspicions of sabotage by bad actors, countries and companies involved said on Monday.

Cables connecting Finland with Germany, and Lithuania with Sweden, have been disrupted, just weeks after the United States warned that it had detected increased Russian military activity around key undersea cables.