Russia's Gazprom has said that gas had stopped leaking from three ruptured Nord Stream gas lines under the Baltic, and that it might be possible to resume pumping through the remaining single line.

In a statement, it said the pressure in the three lines had stabilised and it was working to reduce environmental risks.

Europe launched investigations after major leaks were discovered in the two Russian Nord Stream gas pipelines, each consisting of a pair of lines. Germany, Denmark and Sweden said they believed there had been sabotage.

Nord Stream 1 reported a significant pressure drop on both of its lines, presumed to be caused by ruptures, while Nord Stream 2 reported a similar sharp pressure drop in its 'A' line.

Gazprom said Nord Stream 2's 'B' line could still export gas to Europe, if a decision were made to start deliveries.

Nord Stream 1 had been fully functional before Russia reduced and then stopped gas flows over the past six months, citing non-payment in Russian roubles and technical problems.

But the recently completed Nord Stream 2 has never come online, since Germany, where it makes landfall, froze the authorisation process as Russia was preparing to invade Ukraine.

"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," it said.