Russia has demanded that Japan pay for the return of a crab boat and the release of its crew, after the vessel was seized in the Sea of Japan on Jan. 27, a Japanese source said Wednesday.

Japan is negotiating with Russia over the issue. It is not clear how much money Russia has demanded from the fishery firm that owns the Yoshi Maru No. 38, which was seized along with its skipper and nine crew on suspicion of poaching in its exclusive economic zone.

If the owner of the boat, Hiyoshi Suisan, accepts the demand for payment and remits the money, Russia would have to swiftly release the captain and crew based on the U.N. Convention on the Law of the Sea.

But if the company thinks the sum demanded is too much, it could also file a lawsuit with the International Tribunal for the Law of the Sea in Hamburg, Germany.

Russian border guards started procedures last month to impose an administrative penalty on the company on suspicion of illegal fishing.