New intelligence reviewed by US officials suggests that a pro-Ukrainian group carried out the attack on the Nord Stream pipelines last year, a step towards determining responsibility for an act of sabotage that has confounded investigators on both sides of the Atlantic for months.

US officials said that they had no evidence President Volodymyr Zelensky of Ukraine or his top lieutenants were involved in the operation, or that the perpetrators were acting at the direction of any Ukrainian government officials.

The brazen attack on the natural gas pipelines, which link Russia to western Europe, fuelled public speculation about who was to blame, from Moscow to Kyiv and London to Washington, and it has remained one of the most consequential unsolved mysteries of Russia’s year-old war in Ukraine.

Ukraine and its allies have been seen by some officials as having the most logical potential motive to attack the pipelines.

They have opposed the project for years, calling it a national security threat because it would allow Russia to sell gas more easily to Europe.

Ukrainian government and military intelligence officials say they had no role in the attack and do not know who carried it out. After this article was published, Mykhailo Podolyak, a senior adviser to Zelensky, posted on Twitter that Ukraine “has nothing to do with the Baltic Sea mishap”.

He added that he had no information about pro-Ukrainian “sabotage groups.”

US officials said there was much they did not know about the perpetrators and their affiliations.

The review of newly collected intelligence suggests they were opponents of President Vladimir V. Putin of Russia but does not specify the members of the group, or who directed or paid for the operation.

US officials declined to disclose the nature of the intelligence, how it was obtained or any details of the strength of the evidence it contains.

New York Times News Service