European officials are looking toward Russia after two submarine internet cables in the Baltic Sea were suddenly disrupted in an apparent sabotage operation, just weeks after the United States warned that Moscow was likely to target critical undersea infrastructure.

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

Telecom cables linking two Nordic countries with Germany and Lithuania were cut at the bottom of the Baltic Sea, raising suspicion of sabotage, various media outlets reported on Nov. 18. While the circumstances of the incident remain unclear, the reports ...