After Zelenskiy's justice and energy ministers quit on Wednesday amid the investigation into alleged energy sector graft, the government fired the vice president of Energoatom, the state-owned nuclear power company believed by investigators to be at the centre of the kickback scheme.
The heads of Energoatom's finance, legal and procurement departments and a consultant to Energoatom's president were also dismissed in the clear-out, Prime Minister Yuliia Svyrydenko said.
A Kyiv court has begun hearing evidence from anti-corruption watchdogs whose 15-month investigation, including 1000 hours of wiretaps, has brought the detention of five people and implicated another seven in the scheme that allegedly earned about $US100 million ($A152 million).
Tymur Mindich, a co-owner of Zelenskiy's Kvartal 95 media production company, is the conspiracy's allleged mastermind.
His whereabouts are unknown.
The investigation has prompted questions about what the country's highest officials knew of the scheme.
It has also awakened memories of Zelenskiy's attempt last summer to curtail Ukraine's anti-corruption watchdogs.
He backtracked after widespread street protests in Ukraine and pressure from the European Union, which has pushed the country to address entrenched corruption.
While Ukrainians expressed anger and disbelief at the unfolding scandal, European Commission President Ursula von der Leyen said the EU would disburse a six billion euros ($A11 billion) loan to Ukraine on Thursday and promised more money for the government.
"We will cover the financial needs of Ukraine for the next two years," she said in a speech to the European Parliament.
The EU and other foreign partners have poured money into Ukraine's energy sector.
Russia has relentlessly bombarded the power grid, which requires repeated repairs.
The EU is looking into how it can come up with more money for Ukraine, either by seizing frozen Russian assets, raising funds on capital markets or having some of the 27 EU countries raise the money themselves.
German Chancellor Friedrich Merz stressed EU concerns about corruption in Ukraine when he spoke by phone with Zelenskiy on Thursday.
Merz "underlined the German government's expectation that Ukraine press ahead energetically with fighting corruption and further reforms, particularly in the area of the rule of law," Merz's office said in a statement.
Zelenskiy, the statement said, promised "full transparency, long-term support for the independent anti-corruption authorities and quick further measures in order to win back the confidence of the Ukrainian population, European partners and international donors".
Meanwhile, General Oleksandr Syrskyi, Ukraine's top military commander, visited units fighting to hold Pokrovsk in the eastern Donetsk region and co-ordinate operations in person, he said on the messaging app Telegram.
Ukrainian troops are locked in street battles with Russian forces in the city and fighting to prevent becoming surrounded by a bigger Russian force as Russia's war of attrition slowly grinds across the countryside.
Syrskyi said the key goals are to regain control of certain areas of the city as well as protect logistic routes and create new ones so that troops can be supplied and the wounded can be relocated.
"There is no question of Russian control over the city of Pokrovsk or of the operational encirclement of Ukraine's defence forces in the area," Syrskyi said.
Also on Thursday, Ukrainian forces used a new domestically produced cruise missile as well as other weapons to strike "several dozen objects" in Russian-occupied territories and inside Russia itself, according to the general staff.
