Two Russian sailors being held in the Mozambique port of Maputo are financial hostages in a dispute between the ship’s owner and its local customer, Russia’s foreign ministry told the state RIA news agency in remarks published on Sunday.

Russia’s SHOT news outlet reported last week on its Telegram that two Russians, a Lithuanian and two Ukrainians have been locked up on board a Cameroon-flagged fishing boat Volopas for eight months.

“They found themselves hostage to a financial and property dispute between the ship-owning company and a local agent company,” Russia’s foreign ministry told RIA.

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Diplomatic efforts to repatriate the sailors have not been successful so far, the foreign ministry said.