The North Atlantic Treaty Organization is threatening to retaliate against those responsible for the damage to the natural gas pipes.
NATO said in a statement that the leaks were of deep concern and would be met with a determined response.
The current information shows that this is the result of deliberate, reckless, and irresponsible acts of sabotage. Shipping and the environment are at risk from these leaks. The statement said that they supported the investigations to determine the cause of the damage.
Allies have committed to prepare for, deter and defend against hybrid tactics by state and non-state actors. Allies' critical infrastructure would be attacked with a determination and united response.
The statement was made after the Swedish coast guard said a fourth leak had been found.
The coast guard said that two of the four were in Sweden's exclusive economic zone and the other two were in the Danes' zone.
On Monday, a leak was found in the second part of the Nord Stream 2.
The protection of critical infrastructure in NATO countries was addressed by the NATO secretary-general during his meeting with the Danes.
Russia has a large military presence in the Baltic Sea region.
Norway, now the EU's biggest gas supplier, has deployed its military to protect oil and gas installations as tensions escalate, according to the Financial Times.
John Brennan, the former CIA director, told CNN on Wednesday that Russia is the most likely culprit in the leaks.
The CIA told Germany that it could be attacked, according to a report.
The coast guard of Sweden did not reply immediately.