The political drama was an unwelcome distraction for Zelenskiy as Ukraine's war with its bigger neighbour stretches into its fifth year.
Investigators are conducting an operation to expose a criminal organisation allegedly led by a sitting and a former MP, involving senior officials from the presidential office and other individuals, according to Ukraine's National Anti-Corruption Bureau and the Specialized Anti-Corruption Prosecutor's Office.
Further details would be released later, the agencies said on Wednesday.
Zelenskiy made no public comment on the investigation but issued a decree dismissing Iryna Mudra from the position of deputy head of the Office of the President.
The Ukrainian leader remains dogged by high-level graft investigations.
In 2025, his chief of staff Andriy Yermak resigned and was later named as a suspect in a major graft probe involving a construction project in the biggest threat to Zelenskiy's government since Russia's invasion in February 2022.
Also in 2025, a major embezzlement and kickbacks scandal involving the state-owned nuclear power company brought the resignations of Ukraine's justice and energy ministers.
Zelenskiy is already under pressure over his firing in July of defence minister Mykhailo Fedorov, one of the longest-standing members of his team and a close ally since he helped Zelenskiy win the 2019 presidential election.
Zelenskiy, seeking to reconcile tensions between the defence ministry's young and tech-savvy innovators and Ukraine's seasoned, Soviet-trained battlefield leaders, risked angering both sides by reshuffling his wartime leadership.
He ousted both Fedorov, whose changes to military procurement aimed to stamp out corruption, and commander-in-chief General Oleksandr Syrskyi.
The move sparked days of street protests in support of Fedorov.
For Zelenskiy, it was the second time in a year that a wartime decision triggered a strong public backlash, after he moved in mid-2025 to curb the powers of anti-corruption agencies.
Fedorov, in a video address posted to YouTube late Tuesday, called for elections to be held in Ukraine in a bombshell statement that appeared to directly confront Zelenskiy, who says a ballot cannot be held under the martial law that is in place due to the war.
"We must find a legal, safe and realistic mechanism that will allow Ukraine to restore a full democratic process even amid a prolonged war," Fedorov said.
He said Ukraine faced a systemic crisis in how it was governed, arguing the system was oriented towards protecting itself and resisting change.
He also condemned corruption among officials without naming anyone, saying it had weakened Ukraine's ability to fight the war.
Ukraine's parliament approved Zelenskyy's candidate, Yevhenii Khmara, as the new defence minister in a vote on Wednesday, a move that effectively closes the door to Fedorov's return to the post, which he has sought, any time soon.
MP also gave their consent for Andrii Sybiha to stay on as foreign minister after holding the post in an interim role.
The political disarray comes after recent successes in the war for Ukraine.
Using its innovative drone technology, it has repeatedly hit Russian oil facilities, causing fuel shortages.
It has also shocked the Russian public by striking warehouses of Wildberries, Russia's biggest online retailer, and stalled frontline advances by Russia's bigger army.
But Zelenskiy has been unable to get traction in US-led peace efforts, and Ukraine is at the mercy of Russia's ballistic missiles because more US-made Patriot interceptors are not available due to low stockpiles.
In its latest strike on oil facilities, a drone hit a refinery in Ufa in Russia's Bashkortostan, governor Radiy Khabirov said, a city that is 1300km east of the border with Ukraine.
In Ukraine, a Russian drone attacked a minibus in the southern Kherson region on Wednesday morning, killing four people, the Kherson regional military administration said.
Amid the fighting, Russia and Ukraine each sent home 103 prisoners of war on Wednesday, according to Zelenskiy and the Russian defence ministry.
