A fourth leak has been detected in the Nord Stream 1 and 2 gas pipelines from Russia to Germany, with still no firm indications of what or who might have caused the damage.

Two of the leaks are located in Sweden’s Exclusive Economic Zone and two in Denmark’s, the Swedish coastguard’s command centre told the DPA news agency on Thursday.

Powerful blasts were recorded in the Baltic Sea on Monday, the same day that pressure on both pipelines dropped, prompting accusations from European countries of sabotage.

Three of the four leaks are located within a few kilometres of each other, the Swedish Coastguard said.

“There are currently two gas leaks in Swedish waters, a larger leak above North Stream 1 and a smaller leak above Nord Stream 2,” the coastguard statement said.

The two leak points in Sweden’s Exclusive Economic Zone are just one nautical mile apart, or just under 1.8 kilometres.

The distance from the smaller Swedish leak on Nord Stream 2 to the closest leak in Danish waters is 2.6 nautical miles.

Neither pipeline was in operation but contain natural gas — composed mostly of methane — that has been rapidly escaping.

The Danish Energy Agency said the lines are expected to be completely empty by the weekend and that the leaks correspond to about one third of Denmark’s total emissions in a year.

The unexplained incidents come amid tensions between Europe and Russia over the war in Ukraine.

Russia has throttled gas supplies, throwing energy markets into disarray and triggering fears about a supply crunch as cold weather approaches.

Russian President Vladimir Putin called the leaks an “act of international terrorism”.

According to the Kremlin, President Putin spoke of “unprecedented sabotage” during a telephone conversation with Turkish President Recep Tayyip Erdogan on Thursday.

President Putin said Russia has requested an urgent debate on the matter at the United Nations Security Council in New York on Friday, when he is also to make the annexation of Russian-occupied regions in Ukraine official.

Top European Union officials have threatened punishment for whoever was behind the leaks but have so far not attributed blame.

Lithuania’s Foreign Minister Gabrielius Landsbergis on Thursday described the damage to the pipelines as an “act of terrorism”.

“Another leak is further evidence that this is a premeditated act, an action that I think certainly has the right to be called a terrorist act,” he told parliament.

The Kremlin on Thursday reiterated that it was not behind the damage to the pipelines, and also suggested that it was sabotage.

“Naturally it is hard to imagine that such a terrorist act could have taken place without the involvement of a state actor,” Kremlin spokesman Dmitry Peskov said.