The pressure drop on both Nord Stream strings allows us to confidently assume that the leakage of the gas pipeline is caused by physical damage, and the locations of damage are in the exclusive economic zones (EEZ) of Denmark and Sweden, respectively, according to Nord Stream AG, the pipeline's operator.

"The significant pressure drop caused by the gas leak on both lines of the gas pipeline registered yesterday leads to a strong assumption of the pipeline physical damage," the company said in a statement.

Nord Stream AG immediately informed the relevant coast guard authorities about the incident.

"The positions of two assumed damages have been identified and are located north-east from Bornholm in Swedish and Danish EEZ, respectively," the operator added.

CIA warned Germany about possible attacks on Nord Stream Pipelines: Reports

The CIA warned Germany in the summer about possible attacks on the Nord Stream 1 and 2 gas pipelines, according to media reports.

According to sources familiar with the matter, the US alerted Germans only weeks before pipeline operators reported a drop in pressure readings at both pipelines.

A German government spokesperson refused to comment on the activities of foreign intelligence agencies.

Nord Stream 1 was delivering natural gas from Russia to Germany before being shut down by Gazprom in August, while Nord Stream 2 was never turned on, but both were filled with gas. Denmark announced on Monday that gas was leaking from offshore gas pipelines in the Baltic Sea.

Read next: US ready to support Europe after Nord Stream pipeline leaks: WH

Earlier today, the Swedish National Seismic Network (SNSN) reported powerful underwater explosions in the area of gas leaks from the Nord Stream pipeline.

SNSN Director Bjorn Lund said as quoted by SVT that "there are no doubts that these were explosions."

“One explosion had a magnitude of 2.3 and was registered by dozens of monitoring stations in southern Sweden,” he stated. “You can clearly see the waves bounce from the bottom to the surface," Lund added.

On his part, Peter Schmidt, an Uppsala University seismologist, said the Swedish National Seismic Network recorded two "massive releases of energy" shortly prior to, and near the location of, the gas leaks off the coast of the Danish island of Bornholm.

"The first happened at 2:03 am (0003 GMT) just southeast of Bornholm with a magnitude of 1.9. Then we also saw one at 7:04 pm on Monday night, another event a little further north and that seems to have been a bit bigger. Our calculations show a magnitude of 2.3," Schmidt said.

The Norwegian Seismic Array (NORSAR) also confirmed it had registered "a smaller explosion" in the early hours of Monday, "followed by a more powerful one on Monday evening."

Photos taken by the Danish military on Tuesday showed large masses of bubbles on the surface of the water emanating from the three leaks located in Sweden's and Denmark's economic zones, spreading from 200 to 1,000 meters (656 feet to 0.62 miles) in diameter.