Ukraine's popular ex-defence minister Mykhailo Fedorov has called for wartime elections, in what is widely seen as the biggest challenge to Volodymyr Zelensky's presidency since Russia's full-scale invasion four and a half years ago.
"Democracy cannot be held hostage by Russia," said Fedorov, 35, in a video posted to YouTube on Tuesday, adding that Ukraine is fighting "precisely because we want to remain a free European state".
Since the war broke out in 2022 Ukraine has been under martial law, meaning elections are suspended.
Fedorov, who did not mention Zelensky by name in the video, was unexpectedly fired from his role as defence minister last month, just six months after his appointment.
Zelensky is yet to respond to the video from Fedorov, whose dismissal sparked protests across the country.
About 100 protesters gathered outside the Ukrainian parliament on Wednesday morning, chanting "bring back Federov as minister of defence" and "we are fed up, we want dialogue".
Fedorov is a charismatic politician, and during his tenure as defence minister, he was credited with energising the ministry, heading a drive against corruption, challenging outdated military structures and transforming the battlefield with new technology.
His dismissal in mid-July is believed to have resulted from tensions between him and army commander-in-chief, Oleksandr Syrskyi.
Within days Syrskyi was also replaced, as mounting protests calling for Fedorov's reinstatement piled pressure on the Ukrainian president.
The ousted minister was offered other posts in the government, including deputy prime minister for military innovation, but he made clear he would only return as defence minister.
Hours before he posted his video late on Tuesday, Zelensky confirmed he had asked parliament to confirm acting defence minister Yevhenii Khmara in the post. A vote was due to be held later on Wednesday.
Fedorov spoke in the video of a sense of injustice, warning it was "particularly dangerous when society develops the feeling that the main criterion for an appointment is not professionalism, results, or the ability to transform the country, but personal loyalty to the system".
The protests have continued weekly, with younger Ukrainians especially disappointed to see the established armed forces chief favoured over the fresh-faced digital innovator.
He gave no indication of his own political plans in the YouTube video, instead focusing on the need for a "legal, safe, and realistic mechanism that will allow Ukraine to restore a full democratic process even amidst a prolonged war".
In the space of a month, he has gone from saying he would only return to government in his old job, to calling for widespread reform and political change. He has not explicitly stated his intention to run against Zelensky but he has laid down the most serious challenge yet, calling for "a state where institutions are stronger than names".
That might be a reference to Zelensky's own personal profile, but after such a stark intervention, it is Fedorov's name that his now doing the rounds.
His call for elections has angered some Ukrainian commentators, including those who backed Fedorov's return as defence minister. One of Zelensky's detractors argued that even the government's fiercest opponents understood that holding elections during the war was impossible.
Ivan, 24, who was among the protesters calling for Fedorov's reinstatement outside parliament, told the BBC that "elections at this time of war wouldn't be the best thing".
Zelensky's five-year presidential term ended in May 2024, but under Ukraine's constitution no elections can be held while martial law is in place.
When US President Donald Trump suggested last year that Kyiv was "using war" to avoid a vote, Zelensky said Ukraine was "ready for elections" within 60-90 days if its allies helped guarantee security for them.
Holding a fair and safe vote would present considerable challenges for a country under repeated Russian bombardment and many Ukrainians saw Trump's remarks as reflecting Vladimir Putin's narrative that Zelensky is not a legitimate leader.
In the latest Russian attack on Wednesday, four people were killed when a drone hit a minibus in the southern city of Kherson. Buses and minibuses in Kherson have been repeatedly targeted in recent months, killing drivers and passengers alike.
Mykhailo Fedorov argued that Ukraine was facing a "systemic crisis of governance" and was "scared of change", and pointed to corruption in Ukraine as one of the things hurting the country's war effort.
Oleksandr Merezhko, an MP loyal to Zelensky, said he had backed Fedorov's return to the defence ministry but found his idea for new elections as "very dangerous and unrealistic".
"It will weaken the country and our unity, our resilience. That's why I think that the idea to hold elections unfortunately plays into the hands of Putin."
However, opposition MP Volodymyr Aryev disagreed, accusing Zelensky of being detached from reality and saying "we have reached a point where we must choose between elections and chaos".
