The NATO alliance issued a joint statement calling the Nord Stream pipeline leaks a "deliberate, reckless" act of sabotage Thursday and urged an investigation.

The NATO statement came hours after a fourth leak was discovered along the Nord Stream 1 and 2 pipeline systems Thursday. The first three leaks all occurred and were discovered within 24 hours on Tuesday.

"The damage to the Nordstream 1 and Nordstream 2 pipelines in international waters in the Baltic Sea is of deep concern," NATO wrote in a statement. "All currently available information indicates that this is the result of deliberate, reckless, and irresponsible acts of sabotage."

"These leaks are causing risks to shipping and substantial environmental damage," the statement continued. "We support the investigations underway to determine the origin of the damage."

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The Nord Stream 1 and 2 pipeline systems lie at the bottom of the Baltic Sea. Two of the four leaks were discovered in Sweden's exclusive economic zone, while the other two were in Danish waters. Sweden discovered one hole in its NS1 pipes and the other hole in its NS2 pipes. Denmark experienced the same.

Seismologists say they recorded explosions near the pipelines prior to the leaks.

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Neither pipeline system was in operation at the time of the explosions. NS1 had been operating at just 20% capacity since July and stopped service entirely at the end of August. Operators stated that international sanctions against Russia had made maintenance impossible.

NS 2, meanwhile, has never entered official operation as Germany declined to certify its completion last year. The project was stopped altogether just days ahead of Russia's invasion of Ukraine on February 24.

Accusations have flown across Europe and the world following the leaks, with Ukraine arguing Russia is to blame. Moscow dismissed the accusation on Wednesday.

"It's quite predictable and also predictably stupid to give voice to these kinds of narratives — predictably stupid and absurd," Peskov said. "This is a big problem for us because, firstly, both lines of Nord Stream 2 are filled with gas — the entire system is ready to pump gas and the gas is very expensive ... Now the gas is flying off into the air."

"Are we interested in that? No, we are not, we have lost a route for gas supplies to Europe," he continued.