Danish Prime Minister Mette Frederiksen "cannot rule out" sabotage in connection with leaks at the Nord Stream pipelines, Reuters reports.
Frederiksen spoke after reports of simultaneous problems with the Nord Stream 1 and Nord Stream 2 pipelines.
Officials said the leaks did not pose a threat to energy supplies, and experts said the environmental impact would be limited.
Danish authorities announced Monday that a leak had been discovered in the Nord Stream 2 pipeline, which has never been used. They were later informed of a significant drop in pressure in Nord Stream 1, which until recently was a key source of gas for Germany.
The Swedish Maritime Administration said Tuesday that two leaks had been detected in the Nord Stream 1 pipeline, which runs partially in Swedish waters. Danish authorities also confirmed the leaks.
The Danish Maritime Authority has issued a navigational warning and set up an exclusion zone to ensure that ships do not pass near the leak sites.