The Swedish Coast Guard has reportedly discovered a fourth leak from the Nord Stream gas pipeline.

The coast guard said it located the leak after two pipelines leading from Russia to Germany were damaged in a total of three places, Swedish newspaper Svenska dagbladet reported.

"Two of these four damages are in Sweden's exclusive economic zone," Coast Guard spokeswoman Jenny Larson told the newspaper. The other two claims are located in the Danish exclusive economic zone.

A British Defense Force source told Sky that the pipeline leak in the Baltic Sea was linked to the use of remotely detonated underwater explosive devices.

He added that the mines could have been lowered to the seabed on a long rope, dropped over the side of a ship or placed next to a gas pipeline by an underwater drone months or even years ago.

When the first gas leak was discovered, gas had already been leaking into the Baltic Sea for three days. Sweden's National Seismological Center previously said stations had registered "strong undersea explosions" in the area where the gas leak occurred.

"There is no doubt that these are explosions," said Björn Lund, a seismologist at Uppsala University, which is part of Sweden's national seismic network.