The European Union considers sabotage to be the likely cause of the leaks in the Nord Stream 1 and 2 gas pipelines and has threatened to take countermeasures.
"All available information indicates that these leaks are the result of a deliberate act," said EU foreign policy chief Josep Borrell on Wednesday on behalf of the 27 member states.
Any intentional disruption to Europe's energy infrastructure will "be met with a robust and collective response."
EU Commission President Ursula von der Leyen had previously threatened potential perpetrators with severe consequences.
"Any intentional disruption of active European energy infrastructure is unacceptable and will result in the strongest possible response," von der Leyen tweeted late Tuesday evening.
She spoke to the Danish Prime Minister Mette Frederiksen about the "sabotage action".
"It is of the utmost importance to investigate the incidents now and get full clarity on what is happening and the reasons why.
A total of three leaks were discovered in one of the tubes of Nord Stream 2 and in both tubes of the Nord Stream 1 pipeline after an initial pressure drop on Monday night.
As early as Tuesday, Poland, Sweden, Denmark and Russia considered an attack on the European gas infrastructure to be the cause of the unprecedented damage to both pipelines.
From the point of view of German security circles, there was much to be said for sabotage.
If it was an attack, only a state actor would come into question in view of the effort, it said.
Although gas is currently not being delivered through any of the pipelines, the gas price has risen due to the uncertainty.
Swedish Prime Minister Magdalena Andersson said on Tuesday evening that the information was far from complete, but two explosions had been identified that caused three leaks.
Based on Swedish and Danish information, the conclusion is that it was probably an intentional act.
"So it's probably a question of sabotage," she said.
Habeck: Was an "attack on the infrastructure"
The Danish government made a similar statement.
The authorities had come to the clear conclusion that the acts were intentional and not an accident, Prime Minister Frederiksen said in the evening.
Several explosions were observed within a short period of time.
There is still no information about who is behind it.
The incidents occurred in international waters in the exclusive economic zones of Denmark and Sweden off the Baltic Sea island of Bornholm.
According to a spokesman, the government in Moscow did not want to rule out any variant.
The operator of Nord Stream 2 was skeptical: the lines had been laid in such a way that it was highly unlikely that several lines would be damaged at the same time, for example by a single ship accident.