HAMBURG, Oct. 14 -- A Ukrainian former military officer who denies any part in the attack sat in a German courtroom on Wednesday as a federal prosecutor told judges that the destruction of the Nord Stream pipelines was carried out "on the orders of Ukrainian state agencies," the first time the case has been heard in open court.

The defendant, identified under German privacy rules only as Serhii K., is charged as an accomplice to a war crime at the Hanseatic Higher Regional Court. He says he is innocent. The court has set two hearings a week until at least February, according to Radio Free Europe/Radio Liberty. The trial follows the charges over Nord Stream sabotage that Germany announced in July.

The case now rests on a claim bigger tha...