U.S. allies warned of “hybrid warfare” Tuesday after two undersea communication cables were severed in the Baltic Sea, raising suspicions that they may be the latest acts of sabotage targeting the West as it clashes with Russia.

German Defense Minister Boris Pistorius said Tuesday that “no one believes that these cables were cut accidentally” after a rupture in a 730-mile cable linking Germany and Finland was detected Monday.

 
 

“We have to state, without knowing specifically who it came from, that it is a ‘hybrid’ action,” he said. “And we also have to assume, without knowing it yet, that it is sabotage.”

Lithuania’s navy said Tuesday that it had increased monitoring of its waters after damage to a separate cable connecting the Baltic nation with Sweden’s Gotland Island was detected Sunday.

Swedish operator Arelion said Monday that the company was “in contact with Swedish authorities and the Swedish Armed Forces regarding the incident.”

Later the Swedish Prosecutor’s Office said in a statement that it was launching a preliminary investigation into “suspected sabotage.”

 

The parties involved in both ruptures all members of NATO stopped short of pointing fingers, but eyes immediately turned to Russia.

The news came as President Vladimir Putin formally lowered the threshold for his country’s use of nuclear weapons, days after the United States allowed Ukraine to strike inside Russia using American missiles. And Nordic countries released new guidance advising residents on how to survive a war or similar crisis.

“European security is not only under threat from Russia’s war of aggression against Ukraine, but also from hybrid warfare by malicious actors,” the foreign ministers of Germany and Finland said in a joint statement Monday.

A spokesperson for the U.S. State Department said that in general, U.S. officials are concerned about hybrid warfare and have been in close coordination with allies around the globe.

Western officials have accused the Kremlin of intensifying a campaign targeting Ukraine’s allies while assaulting its neighbor in a war that reached 1,000 days on Tuesday.

“Russia is systematically attacking European security architecture,” the foreign ministers of Germany, France, Poland, Italy, Spain and the U.K. said in a joint statement.