The German navy is helping Norway to protect critical maritime infrastructure such as oil rigs, undersea cables, and pipelines, and is ready to do the same off the Danish and Swedish coasts, its head said on Thursday.

Bordering Russia in the north, Norway is Europe’s biggest producer of natural gas and oil and has an extremely long coast that is hard to protect. It operates an extensive network of pipelines that connect the country with Britain and Europe.

NATO has pledged to boost the protection of critical infrastructure after the ruptures in September in the Nord Stream 1 and Nord Stream 2 gas pipelines, laid on the bed of the Baltic Sea from Russia to Germany.

Norway’s prime minister also said it would deploy its military to protect its oil and gas installations. Sweden and Denmark have both concluded that four leaks on Nord Stream 1 and 2 were caused by explosions, but have not said who might be responsible.

Russia’s defense ministry said on Saturday that British navy personnel blew up the pipelines, a claim that London said was false.

In mid-October, the secretary-general said NATO had already doubled its presence in the Baltic and the North Seas to over 30 ships supported by aircraft and undersea activities.

Details of which ships are deployed where are not usually given. German navy chief Vice-Admiral Jan Christian Kaack said in a statement Berlin had three frigates and a supply ship with some 700 sailors for exercises in the Norway region that would also help monitor the situation, coordinated with NATO.

Kaack said the navy was making good on Chancellor Olaf Scholz’s promise to support Norway, Denmark and Sweden in protecting their maritime infrastructure after the Nord Stream incidents.

“With its presence in Norwegian waters, the German navy is fulfilling NATO’s pledge of ‘one for all, all for one’,” he said. He said overflights by maritime patrol aircraft would also contribute to establishing situational awareness.

Sweden sent a diving vessel on Monday to the site of Russian gas pipelines in the Baltic Sea that ruptured last week following blasts in the area, to probe an incident that has added new tension to Europe’s energy crisis.

Europe is investigating what caused three pipelines in the Nord Stream network to burst in an act of suspected sabotage near Swedish and Danish waters that Moscow quickly sought to pin on the West, suggesting the United States stood to gain.

“The coast guard is responsible for the mission, but we are supporting them with units,” a spokesperson for the Swedish navy, Jimmie Adamsson, told Reuters. “The only one we are naming is HMS Belos, which is a submarine rescue and diving vessel.”

The Swedish coast guard said Nord Stream 1 had stopped leaking, but an overflight suggested gas was still draining out of Nord Stream 2 and bubbling to the surface over a 30 metre (32 yard) radius.

The Kremlin on allegations that the West was to blame for the ruptures on Monday, saying that the United States was able to increase sales and prices of its liquefied natural gas (LNG) as a result.

Washington has strongly denied any involvement. European countries suspect sabotage, but have declined to say who could be behind it.

Kremlin-controlled Gazprom GAZP.MM also said flows could resume at the last remaining intact pipeline in the Nord Stream 2 network, a suggestion likely to be rebuffed given Europe blocked Nord Stream 2 on the eve of Russia’s invasion of Ukraine in February.

“If a decision is made to start deliveries through Nord Stream 2’s line B, natural gas will be pumped into the pipeline after the integrity of the system has been checked and verified by supervisory authorities,” Gazprom said.

The suggestion follows on Sunday that the Nord Stream network could be repaired, given time and enough funds.

NORWAY SENDS SOLDIERS

Nord Stream has been a flashpoint in the energy standoff between the West and Moscow that has pummelled Western economies and fuelled a cost-of-living crisis.

Russia steadily reduced gas flows via Nord Stream 1 this year before halting them altogether at the end of August, blaming technical difficulties caused by Western sanctions. European countries said Moscow was using energy as a weapon.

Nord Stream 2 was never operational, and Western countries have resisted calls from Russia to drop their opposition to the project.

Jolted by the Nord Stream ruptures, European countries have started strengthening security and surveillance around critical infrastructure that could be vulnerable to attack.

Norway, Europe’s main gas supplier, and a major oil exporter, said it had to guard major onshore oil and gas processing plants.

Italy has strengthened surveillance and controls on underwater energy and telecommunications cables, a source told Reuters.

Focus has also turned to the security of other gas supply lines.

Eni, the biggest importer of Russian gas in Italy, at the weekend said Russia had halted all gas flows through the Tarvisio entry point, though its chief executive on Monday.

The stoppage of flows through the Tarvisio entry point “has absolutely nothing to do with geopolitical factors. It is due to the fact that Gazprom would have to pay a monetary guarantee for the transport of gas from Austria to Italy that was not there before,” Claudio Descalzi said.