A mystery object found by the Nord Stream pipeline could help provide clues about who was behind sabotage attack

• A mysterious cylindrical object was found on the seabed by the Nord Stream 2 pipeline.
• Denmark has invited Gazprom, the Russian energy giant, to inspect it.

Denmark has invited the Russian-controlled operator of the Nord Stream 2 pipeline to help recover a mysterious object found next to it, six months after sabotage attacks struck parts of the pipelines.

Russian President Vladimir Putin said experts believe the object could be a signal antenna used to trigger an explosive in that section of the pipeline, AFP reported.

The Danish energy agency said it is "possible" that the object is a maritime smoke buoy and that it "does not pose an immediate safety risk," the outlet said.

A photo of the cylindrical object was released on Thursday, which authorities discovered on the seabed during an inspection of the last remaining intact Nord Stream pipeline, Reuters reported.

Kremlin spokesman Dmitry Peskov said that it was a positive sign that Denmark had invited Gazprom, the Russian energy giant, to help identify the object.

"It's certainly positive news when the owner of the pipeline is invited to take part in very important phases of the investigation," Peskov said, per Reuters.

"It is critically important to determine what kind of object it is, whether it is related to this terrorist act - apparently it is - and to continue this investigation. And this investigation must be transparent," he said.

Russia has previously been critical of not being allowed to take part in the investigation.

The Danish agency said that it could not begin the recovery operation until it got a response from the pipelines' owners, AFP reported. Russian energy giant Gazprom has a majority stake and German, Dutch, and French companies own the rest.

International authorities have been investigating after a series of underwater bombings struck the gas pipelines in September last year.

It is still unknown who was responsible for the sabotage, and Russia has at times blamed the United States and Britain, without any evidence.

Reports suggested that a pro-Ukrainian group was responsible, based on Western intelligence, but Kremlin spokesman Peskov dismissed the reports at the time and said they were a diversion by "the authors of the attack."

The Ukrainian government has denied any involvement in the attack.

The Nord Stream 1 and Nord Stream 2 pipelines, which transported natural gas from Russia to Germany, were not operational at the time of the attack due to disputes between Russia and the European Union.