The warning came as the Swedish coast guard confirmed a fourth leak on the pipelines off southern Sweden, which is in the process of joining NATO.
The first leaks in the pipelines that extend from Russia to Germany were reported on Tuesday, prompting energy companies and European governments to beef up security.
The fear of further damage to Europe’s energy infrastructure has added pressure on natural gas prices, which had already been soaring.
Russia, a major supplier to Europe, cut off deliveries earlier this year in retaliation for sanctions imposed after its invasion of Ukraine. That has caused widespread economic pain across the continent.
NATO ambassadors said in a statement that “any deliberate attack against allies’ critical infrastructure would be met with a united and determined response.” They refrained from saying who they thought was responsible, even though some allies like Poland, and many experts, have said they believe that Russia is responsible.
“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 envoys said.
Russian naval ships ‘spotted near blast site’
European security officials on Monday and Tuesday observed Russian Navy ships in the vicinity of leaks in the Nord Stream pipelines likely caused by underwater explosions, according to Western intelligence officials and one other source.
It’s unclear whether the ships had anything to do with those explosions, these sources and others said – but it’s one of the many factors that investigators will be looking into.
Russian submarines were also observed not far from those areas last week, one of the intelligence officials said.
In Moscow, Kremlin spokesman Dmitry Peskov dismissed the reports as as “stupid and biased,” adding that “many more aircraft and vessels belonging to NATO countries have been spotted in the area.”
Rising tensions over energy supplies
The rising tensions around energy security in Europe come as Russia prepares to annex four regions of occupied Ukraine, a move widely condemned by the West.
Russian energy giant Gazprom heightened uncertainty around energy supplies on Wednesday by threatening on Twitter to cease dealing with a Ukrainian company that controls one of the two remaining pipelines that ship Russian gas to Europe.
The two lines between Russia and Germany were not in operation. But they were filled with tonnes of methane, a major cause of global warming that is being emitted into the atmosphere and will continue to bubble to the Baltic Sea’s surface, probably until Sunday, according to energy experts.
Two of the leaks are on the Nord Stream 1 pipeline that Russia recently turned off as it ramped up energy pressure on Europe. The other two are on Nord Stream 2, which has never been used. The Danish and Swedish governments have said that they believe the leaks were “deliberate actions.”
According to seismologists, the leaks were preceded by explosions. A first explosion was recorded early on Monday southeast of the Danish island of Bornholm. A second, stronger blast northeast of the island that night was equivalent to a magnitude-2.3 earthquake. Seismic stations in Denmark, Norway and Finland also registered the explosions.