Russia's foreign ministry said on Wednesday the United States had questions to answer over its role in explosions on the undersea Nord Stream gas pipelines last year.

Commenting on a report published earlier on Wednesday that said the United States was involved in the explosions, Russia's Foreign Ministry spokeswoman Maria Zakharova called on the White House to comment on the "facts" that had been presented.

Reuters was unable to verify the report, published by U.S. investigative journalist Seymour Hersh on his blog, alleging U.S. involvement in the explosions.

The White House said on Wednesday that Hersh's account was "utterly false and complete fiction".

Moscow, without providing evidence, has repeatedly said the West was behind the explosions affecting the Nord Stream 1 and 2 pipelines last September - multibillion-dollar infrastructure projects that carried Russian gas to Germany under the Baltic Sea.

Western officials have denied those accusations.

"The White House must now comment on all these facts," Zakharova said in a post on her Telegram page where she summarised Hersh's main claims regarding the alleged U.S. involvement.

Investigators from Sweden and Denmark - in whose exclusive economic zones the explosions occurred - have said the ruptures were a result of sabotage, but have not said who they believe was responsible.

Russia said the countries "have something to hide" and are purposefully blocking Russia out from the investigation.

Construction of Nord Stream 2, designed to double the amount of gas Russia could send directly to Germany under the sea, was completed in September 2021, but was never put into operation after Berlin shelved certification just days before Moscow sent its troops into Ukraine in February.

(This story has been corrected to say that blasts were inside exclusive economic zones of Sweden and Denmark, not in their "territorial waters")

^{Source Reuters}