Ukrainian President Volodymyr Zelensky has vowed to "overhaul" state-owned energy companies, after a major corruption scandal engulfed the country's energy sector.

Around $100 million (£76m) has been embezzled, anti-graft investigators said, causing outrage in a country where Russian attacks have resulted in crippling power outages.

"Alongside a full audit of their financial activities, the management of these companies is to be renewed," Zelensky wrote in a post on X on Saturday. 

Energoatom, the state nuclear company at the heart of the scandal, will have a new supervisory board "within a week," he added. 

Several of those implicated in the scandal have close links to the Ukrainian president.

The scandal is unfolding against the backdrop of escalating Russian attacks on Ukrainian energy facilities, including substations that supply electricity to nuclear power plants.

"I have also instructed government officials to maintain constant and meaningful communication with law enforcement and anti-corruption bodies," Zelensky wrote. 

He also called for the quick appointment of a new head of Ukrhydroenergo, a hydropower generating company, and reforms for oil and gas giant Naftogaz and the nation's Gas Transmission System Operator. 

Two ministers were forced to resign over the corruption scheme and a former business partner of Zelensky was sanctioned earlier this week when the scandal broke.

On Monday, the National Anti-Corruption Bureau of Ukraine (Nabu) and Specialised Anti-Corruption Prosecutor's Office (Sap) said the 15 month-long investigation had revealed several members of the Ukrainian government were involved.

Some of those implicated in the scandal are or have been, close associates of Zelensky's. Among those alleged to be involved are Justice Minister Herman Halushchenko, former Deputy Prime Minister Oleksiy Chernyshov and Timur Mindich - a businessman and a co-owner of Zelensky's former TV studio Kvartal95.

Zelensky has previously said he is committed to cooperate fully with the anti-corruption investigation.

"I have also instructed government officials to maintain constant and meaningful communication with law enforcement and anti-corruption bodies," he said on Saturday.

"The full transparency and integrity in the energy sector remain an absolute priority."

But the scandal has brought Zelensky's commitment to fighting corruption under scrutiny once again. 

In July, he faced backlash after he signed a law limiting the independence of Nabu and Sap. 

The outrage was only quelled by Zelensky's decision to reinstate their freedom, but the debacle prompted criticism from European allies including France and Germany, while ambassadors from the G7 group of nations expressed the desire to discuss the issue with the Ukrainian leadership.