Investigators have found traces of explosives at the site of the damaged Nord Stream gas pipelines, confirming sabotage had taken place, a Swedish prosecutor said on Friday.
Swedish and Danish authorities are investigating four holes in the Nord Stream 1 and 2 pipelines which link Russia and Germany via the Baltic Sea and have become a flashpoint in the Ukraine crisis as gas supplies in Europe run short.
Denmark last month said a preliminary investigation had shown that the leaks were caused by powerful explosions.
"Analysis that has now been carried out shows traces of explosives on several of the objects that were recovered," the Swedish Prosecution Authority said in a statement, adding that the findings establish the incident as "gross sabotage".
It said the continued probe would determine whether it would be possible to identify those responsible.
Cooperation with authorities in Sweden as well as in other countries was going very well, lead prosecutor Mats Ljungqvist said.
The prosecutor's office declined to give further comment, including on which explosives were believed to have been used to damage the pipelines.
Russia will wait until a full damage assessment is done before deciding on repairs, if any, Kremlin spokesman Dmitry Peskov said on Friday.
"The very fact that data has already begun to come in, in favour of confirming a subversive act or a terrorist act... once again confirms the information that the Russian side has," Peskov told his daily call with reporters.
"It is very important not to stop, it is very important to find the one behind this explosion."
Neither Gazprom, nor the Nord Stream 1 and 2 replied to Reuters requests for comment.
Seismologists in Denmark and Sweden previously said they had registered tremors in the immediate vicinity of the leaks and that the signals did not resemble those from earthquakes.
Danish police declined to comment on the Swedish findings.
The Sept 26 ruptures of the seabed pipelines, spewing gas into the ocean that bubbled to the surface in the week that followed, triggered warnings of public hazard and fears of environmental damage.
A section measuring at least 50 metres (164 feet) is missing from Nord Stream 1, Swedish daily Expressen reported on Oct 18 after filming what it said were the first publicly released images of the damage.
Russia's defence ministry last month said that British navy personnel blew up the pipelines, a claim that London said was false and designed to distract from Russian military failures in Ukraine.