Authorities in Europe have seen signs their energy supplies could be under threat. They say damage to gas pipelines under the Baltic Sea are an act of "sabotage."

The Nord Stream pipelines run from Russia to Germany. Last month, Russian officials cut off the flow through one of them. They never put the second into operation. Still, earlier this week, Danish and Swedish authorities detected two underwater explosions, then reported three leaks.

Danish Foreign Minister Jeppe Kofod said all available information suggests the explosions were "intentional." However, he said they don't know who did it or why.

Russian leaders were quick to deny involvement. Presidential spokesperson Dmitry Peskov called allegations against them "predictably stupid and absurd." They say agents with their security service are investigating the damage as "international terrorism."

European Union leaders have seen the fighting in Ukraine cut off the flow of Russian energy and left them scrambling with winter approaching. The leaks will not affect supplies in the short term, but they demonstrate that the EU's infrastructure is vulnerable.