Finnish authorities say they have opened an investigation into the rupture of a data cable under the Baltic Sea, adding to a Swedish probe into the possible sabotage of that link and another cable.

Germany and Finland say they are "deeply concerned" after an undersea cable linking the countries was severed.The rupture of the 1,170km (730-mile) telecommunications cable - which is being investigated - comes at a time of heightened tension with Russia.

The C-Lion1 cable between Finland and Germany was severed in the Baltic Sea, its operator said, after damage was reported to another cable linking Lithuania and Sweden.