Denmark's maritime traffic agency on Monday instructed ships to steer clear of a 5-nautical-mile (9.25-kilometer) radius off of the Danish island of Bornholm after a suspected gas leak overnight from the defunct Nord Stream 2 pipeline.
The gas leak "is dangerous for maritime traffic," the authority said in a notice to ships.
Overnight pressure in the pipeline dropped from 105 bars to 7.
Authorities had spotted a "large bubble field near Bornholm," Nord Stream spokesman Ulrich Lissek said.
Defunct but filled with gas
The Nord Stream 2 pipeline was designed to double the flow of Russian gas directly to Germany.
The project, which was completed in late 2021, was suspended before it entered service shortly before Russia invaded Ukraine.
"The pipeline was never in use, just prepared for technical operation, and therefore filled with gas," Lissek said.
Kremlin representatives have previously suggested that the Nord Stream 2 pipeline should be allowed to go into operation.
It was "technically possible" to continue deliveries, Kremlin spokesman Dmitry Peskov said in August.