The Nord Stream pipeline network, part of which supplies Germany with gas from Russia, has been damaged in three places, its operator has said.
The damage to the system on the bed of the Baltic Sea – all caused in one day – was “unprecedented”, Nord Stream AG added.
The Kremlin said it could not rule out sabotage as a cause of the damage, while other authorities are investigating.
The Danish energy authority also said it could be a deliberate act, as any event like this was “extremely rare”.
And a European security source told Reuters: “There are some indications that it is deliberate damage. You have to ask: Who would profit?”
Meanwhile, a reading from a nearby seismograph, which records vibrations on the planet’s surface, was later found to show spikes at similar times to when the losses in pressure in the pipes were first recorded, according to a German geology research centre.
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‘No doubt these were explosions’
Sweden’s national seismology centre said its measurement stations recorded “powerful subsea blasts” in the area where the gas leaks occurred.
Seismologist Bjorn Lund told public broadcaster SVT: “There is no doubt that these were explosions.”
Earlier, Sweden’s Maritime Authority had issued a warning about two leaks in the Nord Stream 1 pipeline, which until the Ukraine war provided about 60% of Germany’s gas needs.
On Monday, Denmark issued a warning about a leak in the yet-to-be-opened Nord Stream 2 pipeline, which had been built to boost the amount of Russian gas supplied to Germany.
The leak from Nord Stream 2, southeast of the Danish island of Bornholm in the Baltic Sea, prompted the setting up of a five nautical mile exclusion zone, to protect shipping from any danger.
The Danes have now marked off the leak from Nord Stream 1, which is also near Bornholm.
Denmark’s energy authority added it expected the leak will continue for several days and perhaps even a week.
Nord Stream AG said it was impossible to estimate when the gas network system would be working again.
“The destruction that occurred on the same day simultaneously on three strings of the offshore gas pipelines of the Nord Stream system is unprecedented,” it said.
“It is not yet possible to estimate the timing of the restoration of the gas transport infrastructure.”
Nord Stream 1’s twin undersea pipelines opened in 2011, with the ability to supply up to 27.5 billion cubic metres of gas a year each.
But since fallout from Russia’s invasion of Ukraine, and the EU’s determination to cut its reliance on Russian gas, flows through the Nord Stream 1 have reduced to zero.
Russia has been accused of using gas supply as a weapon, something Russia blames on Western sanctions. The German government has withheld the licence of Nord Stream 2 because of Russia’s actions.
Despite not carrying gas to Germany and beyond, both pipelines have apparently remained full of gas, which is now leaking into the sea.
It was not immediately clear what consequences would follow, especially as methane in the atmosphere is a driver of climate change. The EU Commission said it would analyse the potential impact.
German environmental group Deutsche Umwelthilfe said any effects from an explosion would be local and that some gas would dissolve in the sea.
The cut in supplies of Russian gas to Europe is one of the main drivers of higher gas prices that have caused inflation to surge in the UK and elsewhere.
On Tuesday, a ceremony was due to be held to inaugurate a new pipeline, Baltic Pipe, to carry Norwegian gas through Denmark to Poland, which it is hoped will ease some pressure on European gas supplies.