Ferenc Horváth and József Simola resigned "despite engaging in no way whatsoever in the wrongful practices around INA that surfaced in late August", the company said.

They will continue to perform their duties until successors are appointed.

Late in August, Croatian authorities took five people into custody, including the head of INA's gas trade business, Damir Skugor, suspected of defrauding INA of more than HRK 1 billion through gas deals on international markets.

MOL owns a little more than 49% of INA but exercises management rights over the company. The state of Croatia is the other big stakeholder in the company.

Croatia's government has called for the dismissal of INA's entire board over the case of fraud.

A week earlier, INA chairman Sándor Fasimon tendered his resignation "despite no involvement in any of the wrongful practices that surfaced around INA".