Nato’s secretary general Jens Stoltenberg on Tuesday said the Western alliance had doubled its presence in the Baltic and North seas to more than 30 ships supported by maritime patrol aircraft and undersea surveillance after the “sabotage of Nord Stream pipelines”.
He made reference to four leaks in the Baltic Sea caused by explosions on the Nord Stream 1 and 2 pipelines late last month.
“Allies are increasing security among key installations and stepping up intelligence and intelligence-sharing,” Mr Stoltenberg said.
European leaders have described the incidents as state-sponsored sabotage, which pushed Nato member Norway to station military personnel near its oil and gas installations. Russian President Vladimir Putin has accused the West of attacking the pipelines, a claim which the United States has denied.
Mr Stoltenberg, who was speaking before a two-day meeting in Brussels of Nato defence ministers, told reporters that while he could not comment on the Swedish and Danish investigations into the cause of the detonations, Nato was ready to take “the necessary measures if needed”.
“We also stated a few years ago that hybrid and cyber attacks can trigger Article 5,” said Mr Stoltenberg, in reference to the alliance’s mutual defence pact that treats an attack against one member as an attack against all.
“Any deliberate attack against allies’ critical infrastructure would be met with a united and determined response.
“Exactly what kind of measure depends on the nature of the attack and we will never give our potential adversaries the privilege of defining exactly where the threshold for Article 5 goes."
Mr Stoltenberg also said Nato “stands with Ukraine for as long as it takes” and described Russian strikes on Monday and Tuesday on the capital Kyiv as “a sign of weakness”.
“Russia is actually losing on the battlefield,” he said, “so the way they are able to respond is by indiscriminate attacks on Ukrainian cities.”
Mr Stoltenberg said Nato’s routine nuclear exercises were maintained for next week despite several hints made by Mr Putin about the possibility of using nuclear weapons.
“We need to understand that Nato’s firm, predictable behaviour is the best way to prevent escalation,” said Mr Stoltenberg.
He was referring to the annual 'Steadfast Noon' drill, in which Nato air forces practise the use of US nuclear bombs based in Europe with training flights, without live weapons.
Mr Stoltenberg described Mr Putin's nuclear threats as "dangerous and irresponsible".
"Russia knows that a nuclear war cannot be won and must never be fought," he said.
The EU’s foreign and security policy chief Josep Borrell was scheduled to join Nato defence ministers in their last meeting on Thursday.
“Nato and the EU face the same security challenge,” said Mr Stoltenberg. “We have a difficult winter ahead so it’s even more important that North America and Europe continue to stand united in support for Ukraine and in defence of our people.”
Defence ministers meeting at Nato's headquarters later this week will take the decision to increase their stockpile of weapons and ammunitions, Mr Stoltenberg said.
The Nord Stream leaks prompted the EU to ask its 27 member countries to conduct security tests on their critical infrastructure.
Latvia’s Prime Minister Krisjanis Karins told The National last week that the first task was to draw up a list of European assets that could be vulnerable.
He said: “It means, of course, increased costs for overseeing this, but this again, on a co-ordinated level, if we can identify what are the potential vulnerable areas, this is what we have to look for."