Warsaw- The head of Poland's biggest oil refiner resigned Thursday amid reports of disagreement within the management board.

Wojciech Heydel, who had served as CEO since June 7, resigned citing "the superior interest of the company as the current formula for co-operation within the framework of Management Board has been exhausted," the company said in a statement.

Heydel was replaced by Dariusz Krawiec, who had served as the board's vice-president from June 7. Krawiec was also rumoured to be favored by Poland's state treasury.

Heydel served as the Vice-president of the management board for sales from 2004 to 2008. He was the acting president of the board since February before his appointment as CEO. (dpa)