The arrest of multiple people over an alleged Russian plan to assassinate Ukrainian President Volodymyr Zelenskyy is the latest in a long line of reported plots.
The country's security service has said this time a "network of agents" taking orders from the Kremlin's espionage agency were responsible.
Mr Zelenskyy, the comedian-turned-president, has brushed off threats to his life in the past.
But experts say a successful assassination attempt could have far-reaching impacts, both for Ukrainians on the frontline and for global support for the nation's fight.
Here's what we know so far.
'A network of agents' involved in assassination plot
In a post on Telegram, the Security Service of Ukraine (SBU) said it "exposed a network of agents" allegedly getting orders from Moscow.
The two men detained were colonels in Ukraine's State Security Administration — an organisation responsible for protecting the country's most prominent people, including the president.
Officials said the pair had "leaked secret information".
"The enemy was actively developing plans to eliminate President Volodymyr Zelenskyy," security officials said on Telegram.
"One of the tasks of the FSB intelligence network was to search for executors among the military close to the protection of the president, who could take the head of state hostage and later kill him."
A video released by the SBU showed a man alleged to be one of the colonels, with his face blurred describing a potential plot involving blocking Mr Zelenskyy as he attempted to leave his office or another location.
The video has not been verified.
Who is the FSB?
The Federal Security Service of the Russian Federation (FSB) is Russia's primary security agency.
The Moscow-based organisation is responsible for counter-intelligence, counterterrorism, border security, and surveillance.
It is the main successor to the Soviet Committee of State Security, also known as the KGB, which was dismantled in 1991.
The FSB has repeatedly been accused of corruption, fraud and misinformation — it is among a series of Russian groups accused by the White House of playing a role in spreading disinformation ahead of the 2016 US election.
Who is the HUR?
The Main Directorate of Intelligence of the Ministry of Defence of Ukraine (HUR or GUR) is also called the Defense Intelligence of Ukraine (DIU).
It is Ukraine's military intelligence service, led by Lieutenant-General Kyrylo Budanov.
General Budanov has been dubbed the man "without a smile" by Ukrainian news outlets and the "dark prince of the Ukraine war" by the Washington Post.
Who is the SBU?
The Security Service of Ukraine (SBU) is the country's main internal security agency, responsible for counter-intelligence and monitoring organised crime and terrorism.
Its former head, Ivan Bakanov, was dismissed by Ukraine's parliament in July 2022, accused of failing to root out Russian spies within the organisation.
Its current leader is Vasyl Malyk.
The SBU added it had also intercepted another plot to assassinate military intelligence chief Kyrylo Budanov which it said had been planned for "before Easter".
Easter was observed on May 5 in Ukraine this year.
"The enemy's plan was as follows," the SBU alleged on Telegram.
"First, the recruited agent had to observe the movement of the person under guard and pass information to the enemy.
"According to the coordinates of the house where the official was supposed to be, a rocket attack was planned.
"Then they were going to attack the people who remained at the affected area with a drone.
"After that, the Russians planned to target with another missile, including to destroy traces of the use of the drone."
The decision to target Mr Budanov along with Mr Zelenskyy was not surprising to Associate Professor Matthew Sussex, an expert on strategic policy at the Australian National University.
"He's someone who also has a bit of a cult following, someone with a very dry sense of humour," Dr Sussex said.
"He's someone who has been on the front lines, he's orchestrated all sorts of very inventive attacks against Russia, and so he's someone else the Russians are probably keen to target."
SBU head Vasyl Maluk said he had personally monitored the investigation leading up to the arrests, claiming in a statement that the attack was meant to be a "gift to Putin before the inauguration".
Multiple previous alleged assassination attempts
This is not the first time Ukrainian officials have announced a foiled assassination attempt.
Just weeks after Russia's invasion of Ukraine, one of Mr Zelenskyy's top advisers claimed there had been more than a dozen attempts on the president's life.
"We are constantly receiving intelligence that there are certain reconnaissance groups trying to enter government quarters and the like," Mykhailo Podoliak told local media in March 2022.
"We have a very strong network of intelligence and counterintelligence — they are monitoring this situation and these reconnaissance groups are being eliminated on their approach."
In August last year, Ukrainian intelligence services announced they had detained a woman helping Russian authorities plan an air strike on an area Mr Zelenskyy had visited.
The SBU claimed the woman, who lived in the region, used local connections to try and work out the president's itinerary, and captured photos and videos of "Ukrainian facilities".
However, experts at the time told the ABC there were "probably thousands [of people in Ukraine] who are part of a network of Russian intelligence".
The woman was not a part of Mr Zelenskyy's inner circle.
“If I were thinking about it constantly, I would just shut myself down, very much like Putin now who doesn’t leave his bunker,” the Ukrainian leader said in an interview with CNN in mid-2023.
"Of course, my bodyguards should think how to prevent this from happening, and this is their task.
"I don't think about it."
What would losing 'the public face of Ukraine's resistance' mean?
Mr Zelenskyy, a former comedian, became famous in Ukraine for playing a high school teacher who becomes president.
He won the 2019 election in a landslide despite having no prior political experience — before war broke out, he had promised to remain in office for only one term.
He has since become the "public face of Ukraine's resistance", according to Dr Sussex.
"That matters on two levels," he said.
"It matters internally, people associate him with leadership, but more important than that is [that] he's the international face. He goes to lobby for military assistance, to lobby for funds.
"If he wasn't in the picture, sure, there would be someone else who could do the job, but it would be less easy and there would be less overall support for those efforts, particularly among Western publics.
"There's competition for arms ... and being effective in that space is absolutely crucial if you're trying to protect your homeland."
Public support for the Ukrainian president has fallen since the beginning of the war.
Trust in Mr Zelenskyy declined to 62 per cent in December 2023 compared with 84 per cent a year earlier, recent polling by the Kyiv International Institute of Sociology showed.
"Nonetheless, he is the domestic face of the war just as much as he is the international face of the war," Dr Sussex said.
"We're up to something like 19-20 attempts on Zelenskyy's life, so it's obviously something the Russians have been trying to do for a while."
Dr Iryna Skubii, the University of Melbourne's first Mykola Zerov Fellow in Ukrainian Studies, said while there would be an official transferral of power in place, Mr Zelenskyy's death would have "much bigger ramifications".
"The main aim and main goal [for Russia] is to destabilise the situation both in Ukraine and internationally," she said.
"Many things are holding up on President Zelenskyy and his activities abroad, he is very good at getting support and meeting with different leaders worldwide.
"It would have a huge impact on Ukraine both in coming months and in the long run."
A new political leader would mean "disrupting the network" of international support, according to Dr Skubii.
"Establishing new personal contacts and trust between the international leaders and alliances takes time, and Ukraine doesn't have much time at the moment," she said.
International officials, including US Secretary of State Antony Blinken, have previously confirmed there are contingency plans already in place should Mr Zelenskyy be killed.
"The Ukrainians have plans in place — that I'm not going to talk about or get into any details on — to make sure that there is what we would call "continuity of government" one way or another," he told CBS news in 2022.
"And let me leave it at that."
