Staunch Putin ally and Chechen warlord Ramzan Kadyrov is said to have fallen into a coma.
The 49-year-old, who has served as head of Russia's Chechen Republic since 2007, is gravely ill and suffering from kidney failure.
While doctors have not confirmed any details surrounding the severity of his condition, local reports say Mr Kadyrov's relatives have rushed to his bedside as fears behind the scenes grow.
It is believed he is currently undergoing dialysis at a private clinic in the semi-autonomous Muslim republic.
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One report suggested the 49-year-old's condition is so severe that he has slipped into a coma.
According to Ukraine's GUR military intelligence, the process of picking Mr Kadyrov's successor has already begun, with the power to appoint the next Chechen leader lying with Vladimir Putin.
Rumours have swirled that Mr Kadyrov's 20-year-old son, Akhmat, could be handed the role after he was recently appointed as the republic's Deputy Prime Minister.
His other son, 18-year-old Adam, who is his head of security and allegedly his father's "favourite" child, is also believed to be in the running.
Mr Kadyrov has served as head of Russia's Chechen Republic since 2007
|GETTY
However, it remains unknown whether Mr Putin would agree to either of Mr Kadyrov's sons taking control of the region.
The Chechen leader has 15 children with three polygamous wives, and has packed his administration with several of them.
Reports of his seriously ill health come just weeks after he appeared to hint at his impending demise.
Last month, he said: "If you listen to the rumours, I won't live into old age.
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The Chechen leader has been a long-time supporter of the Russian President
|GETTY
Mr Kadyrov has been frequently accused of carrying out numerous human rights abuses
|GETTY
"Well, I don't want to live into old age.
"I want to pass away while everyone loves and respects me. And [remembers me] that way after my death."
Mr Kadyrov has been frequently accused of carrying out numerous human rights abuses, including extrajudicial killings, torture, persecution of gay Chechens and war crimes.
He is one of the most heavily sanctioned people on Earth and faces measures imposed by the US, EU, UK, Canada and Australia.
The 49-year-old has supplied tens of thousands of fighters from Chechnya (pictured) to bolster Mr Putin’s war effort
|GETTY
Mr Kadyrov has been a vocal backer of Russia’s invasion of Ukraine, supplying tens of thousands of fighters from Chechnya to bolster Mr Putin’s war effort.
For several years, persistent reports have circulated claiming the 49-year-old is seriously ill, with speculation pointing towards kidney problems and pancreatic necrosis.
Exiled Russian opposition figure Mikhail Khodorkovsky has alleged that Mr Kadyrov has prepared for the possibility of Mr Putin blocking any succession by his sons, claiming he has been “negotiating with Arab sheikhs” to secure the evacuation of his family and protect his assets.
The 49-year-old is also believed to have refused treatment from Moscow-based doctors, having previously alleged he was “poisoned” by medics in the Russian capital.
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