This comes after the government called on SSH on Friday to provide it with information about the replacement of the Petrol management by 4 November.

Former CEO Tomaž Berločnik and management members Rok Vodnik and Igor Stebrnak resigned in mutual agreement with the supervisory board. The only management member to stay on was workers director Ika Krevzel Panić.

Chief supervisor Nada Drobne Popovič has stepped in as interim CEO, while the head of strategic cost management, Danijela Ribarić Selaković, was appointed third management board member on Thursday.

Differences in implementation of the company's strategy were stated as the official reason for the resignations by Drobne Popovič after the meeting.

But no further details about the changes at what is the country's largest company in terms of revenue have led to a number of speculations.

Some believe that the move was the result of Russian interest to enter Petrol, with Drobne Popovič, who used to serve on the management of SSH, being the CFO of the metalworks company Acroni, a member of the Russian-owned SIJ Group. Drobne Popovič has denied this.

Meanwhile, Prime Minister Marjan Šarec has denied several times in the past days rumours that this was an attempt by the Marjan Šarec List (LMŠ) to strengthen its position in this key company. He also added that other parties had been on the political scene much longer than his.

Brane Golubović of the LMŠ meanwhile said he could not believe that "certain networks" had nothing to do with this, but refused to say anything about who he was referring to.

The Social Democrats (SD) said already on Saturday that they had nothing to do with the move. "The supervisory body is autonomous in its decision-making and is also responsible for its decisions."

Meanwhile, the opposition New Slovenia (NSi) has called a session of the parliamentary Public Finance Oversight Commission, with invitations having been sent out to SSH representatives, Finance Minister Andrej Bertoncelj and the prime minister.

"We're not accusing anybody of doing anything wrong. But it is surprising that a successful management of a state-owned company had to go," said NSi deputy group head Jernej Vrtovec.

The supervisory board of Petrol said in its first response that it acted independently, in accordance with the law, and that "all its members act completely independently as well, and for the company's benefit".

It noted that the decision on the resignation of the management board had been made unanimously, "taking into account the information which it had had at its disposal at the time".

In the press release, the board also said that SSH had "no additional information, like all other shareholders, about the activities of the company's supervisory board related to the early termination of the term".

Some believe that the reason for resignation is to be found in some transactions in the countries of former Yugoslavia, among them the acquisition of the electricity and gas arms of Croatian company Crodux.

Unofficially, the supervisors also took issues with several other planned takeovers in the region, deeming them too demanding financially.

The Association of Small Shareholders meanwhile raised the issue with Petrol failing to provide equal communication of information for all shareholders.