Russia needs permission for its vessels to conduct investigations into explosions that damaged Nord Stream pipelines in the Baltic Sea, Deputy Prime Minister Alexander Novak said on Friday.

He did not specify who should grant the permission, but Nord Stream AG, the operator of the older Nord Stream 1 pipeline, said last week that the owner of a survey vessel it chartered did not have the greenlight from the Norwegian foreign ministry to depart and start assessing ruptures to the pipelines.

“The whole question is in the access for our vessels, which should have rights of passage (to the area of the incidents),” Novak told reporters, commenting on Moscow’s efforts to investigate the damage to the pipelines.

Russia said on Thursday it had summoned diplomats from Germany, Denmark, and Sweden to complain that representatives from Moscow and Gazprom had not been invited to join an investigation into the leaks in the gas pipelines that run from Russia to Europe.

Sweden has previously rejected calls from Russian authorities to be part of the investigation or to share any findings before it is complicated.

The Danish foreign ministry said on Thursday “the Russian wish to participate in the investigation of the Nord Stream leaks has been brought up through diplomatic channels in Moscow and Copenhagen”. The cause of the damage to the Nord Stream pipelines remains unclear, but European Union countries have said they suspect sabotage, while Russia has called the incidents an “act of international terrorism” and blamed the West.

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.

Unexplained gas leaks detected in the Nord Stream 1 and 2 pipelines from Russia to Germany have prompted investigations by European countries into the cause, including possible sabotage.

Denmark’s armed forces on Tuesday released video showing bubbles rushing to the surface of the Baltic Sea above the pipelines, and said the largest gas leak had caused surface disturbance of well over 1 kilometer in diameter.

Here is a breakdown of what is known so far:

What happened?
The operator of the Nord Stream 2 gas pipeline reported a sudden drop in pressure overnight on Monday, with a spokesperson suggesting there could have been a leak.

This was followed by a Danish Energy Authority statement that a leak had likely occurred in one of the two Nord Stream 2 pipelines lying in Danish waters.

A few hours later, Nord Stream AG, operator of another undersea gas pipeline from Russia to Germany, said it was looking into a drop in pressure in Nord Stream 1.

Sweden’s Maritime Authority said on Tuesday it had warned of two leaks on Nord Stream 1 in Swedish and Danish waters.

Each line of the pipeline consists of about 100,000 24-tonne concrete-weight coated steel pipes laid on the seabed. The pipelines have a constant internal diameter of 1.153 meters, according to Nord Stream.

Sections lie at a depth of around 80-110 meters.

Where are the leaks?
Two leaks were detected on the Nord Stream 1 pipeline, which stopped delivering gas to Europe last month, both in an area northeast of the Danish island of Bornholm.

Danish authorities have asked ships to stay clear by a five nautical mile radius off Bornholm after the leak at Nord Stream 2, which has yet to enter commercial operations. The plan to use it to supply gas was scrapped by Germany days before Russia sent troops into Ukraine in February.

Both pipelines still contain gas under pressure.

What caused the leaks?
It is not yet clear. Analysts and experts say such leaks are very rare and Nord Stream AG has called leaks on three strings of the offshore gas pipelines “unprecedented”.

Possible causes range from technical malfunctions, a lack of maintenance or even possibly sabotage.

The Kremlin has said it did not rule out sabotage as a reason behind the damage, adding it was an issue affecting the energy security of the “entire continent”.

Poland’s prime minister said the leaks were an act of sabotage, while Denmark’s leader said it could not be ruled out.

The European Commission said it was premature to speculate.

German Geology Research Centre GFZ said on Tuesday that a seismograph on Bornholm showed spikes at 0003 GMT and 1700 GMT on Monday, when the pressure losses occurred.

Who is investigating?
For the Nord Stream 2 leak, the head of Denmark’s Energy Agency Kristoffer Bottzauw told Reuters said it was too early to say who would conduct the investigations and no-one has been to look at the pipeline yet.

The Swedish Armed Forces, the Coast Guard and the Swedish Maritime Administration and other relevant authorities are taking necessary measures, the Swedish Prime Minister said.

Germany on Monday said it was coordinating a response with police, local officials and the energy agency.

Potential impact?
Gas leaking from the damaged Nord Stream 2 pipeline in the Baltic Sea will continue for several days and perhaps even a week, the Danish Energy Authority said.

Denmark’s armed forces released video showing bubbles rushing to the surface of the Baltic Sea above the Nord Stream 1 and 2 pipelines, and said the largest gas leak had caused surface disturbance of well over 1 kilometer in diameter.

Vessels could lose buoyancy if they enter the area, and there might be a risk of leaked gas igniting over the water and in the air, but there were no risks associated with the leak outside the exclusion zone, it said.

The leak would only affect the environment in the area in which the gas plume in the water column is located and escaping greenhouse gas methane would have a damaging climate impact.

Danish authorities asked that the level of preparedness in Denmark’s power and gas sector be raised after the leaks, a step that would require heightened safety procedures for power installations and facilities.