Multiple countries are investigating and the authorities in Europe say they have not ruled out sabotage. But U.S. intelligence officials have assessed that the cables were not cut deliberately.

Sweden's prime minister says his government has formally asked China to cooperate in explaining the recent rupture of data cables on the Baltic Sea bed in an area where a China-flagged vessel was sighted.

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.