Brussels - (AFP) - The European Union's foreign policy chief, Josep Borrell, said that the European Union considers the gas leak in two undersea pipelines linking Russia to Germany this week "not a coincidence", amid indications of "deliberate action".

And he warned in a statement that "any deliberate tampering with European energy facilities is completely unacceptable and will be met with a strong and unified response."

Borrell called for an investigation into the leakage on Nord Stream 1 and 2, saying that "all available information indicates that these leakages are the result of deliberate action."

"We will support any investigation that fully demonstrates what happened and why, and we will take further steps to increase our resilience in the area of energy security," he added.

"The Nord Stream sabotage appears to be an effort to further disrupt the EU's energy supply," European Council President Charles Michel wrote in a tweet.

"Those behind this will be held accountable," he added.

Sweden and Poland had announced that the leakage from the two gas pipelines in the Baltic Sea was likely caused by acts of sabotage, and Warsaw hinted at the possibility of Russia's involvement with the aim of escalating the war against Ukraine.

The two pipelines are a strategic infrastructure linking Russia with Europe. While the two pipelines are not currently operating, they contain gas, which caused bubbles to appear in the leak that was detected on the surface of sea water in the exclusive economic zones of Sweden and Denmark.

Seismologists in Sweden detected two "massive releases of energy" just before the leak occurred.