COPENHAGEN - A Russian-flagged vessel chartered by Nord Stream AG, the operator of the leaking Nord Stream 1 gas pipeline, is conducting surveys in the area for the first time, the Swedish Navy said on Thursday.

Both Sweden and Denmark have concluded that four Nord Stream leaks were caused by explosions last month but have not said who might be responsible. World leaders have called it an act of sabotage.

Swedish prosecutors and police earlier this month wrapped up a crime scene investigation, but the Nordic country's navy on Wednesday said it would conduct its own survey.

"We are sharing the same space at the moment and communicating with each other," a spokesperson for the Swedish Navy told Reuters on Thursday.

"The consortium stated some time ago that they wanted to do an investigation of the scene of the explosions... In order to just do an underwater survey you don't need any permission from us."

Nord Stream AG, which is majority-owned by Russia's Gazprom, did not immediately reply to a request for comment.

Sweden has rejected calls from Russian authorities to be part of its investigation or to share any findings before it is completed.

The owner of the Nord Stream 2 pipeline has also said it plans to conduct its own investigation but at a later time, the navy spokesperson said.

Norway, now Europe's biggest supplier of natural gas, has increased its pipeline inspections in the wake of the suspected blasts on the Nord Stream system last month, the head of the country's gas supply infrastructure told Reuters.

Dwindling flows of gas from Russia, which once supplied 40% of Europe's needs, has left the European Union struggling to unite over how to respond to surging prices that have deepened a cost-of-living crisis for families and businesses.

(Reporting by Stine Jacobsen in Copenhagen, additional reporting by Vladimir Soldatkin in Moscow, editing by Terje Solsvik and Nick Macfie)