The world “must know the truth” about who was behind explosions affecting Nord Stream gas pipelines, and those responsible should be punished, the Kremlin spokesman said on Thursday, after a U.S. investigative journalist alleged U.S. involvement in last September’s blasts.

Speaking to reporters, Dmitry Peskov also said the blog post by journalist Seymour Hersh should prompt an international investigation into the incidents. The White House on Wednesday dismissed the Hersh report, which said an attack on the pipelines was carried out last September at the direction of U.S. President Joe Biden.