It is part of a preliminary investigation in Ukraine that concerns suspected war crimes, State Prosecutor Håkan Larsson told TT.
Ukraine has requested legal assistance from Sweden. Handing over the ship requires that the suspected crime is also punishable in Sweden.
When we translate the circumstances they have described, we believe that in Sweden it would have been considered a war crime, the state prosecutor says.
According to the Coast Guard, the bulk carrier is listed on Ukraine's sanctions list, "where information indicates that it is transporting grain stolen from Ukraine."
