Sergei Markov said it was “absolutely clear” that the Ukrainian intelligence service carried out the operation to kill 62-year-old Mr Prigozhin – which occurred exactly two months after he led a mutiny against the Russian military – as a “gift” to mark the country’s independence day on Thursday.
The claim has been dismissed by Britain’s former spy chief and experts on Russia, who said that “one way or another”, the Kremlin was involved.
The Wagner chief was among 10 people who died in the accident 180km north-west of Moscow on Wednesday.
This is what we know so far.
The plane carrying three crew members and seven passengers was en route from Moscow to St Petersburg when it went down near Tver on Wednesday.
Russia’s civilian aviation agency, Rosaviatsia, quickly reported that Mr Prigozhin was on the manifest and later said that, according to the airline, he was indeed on board.
The Kremlin and Russian Defence Ministry have not yet commented.
Doubts have been raised as to whether the Wagner leader really is dead. Is he?
There were believed to be two planes owned by Mr Prigozhin in the sky at the time of the accident. One was reportedly seen doing zigzags over Moscow after the crash, according to Flight Radar tracking systems.
Experts have said that while evidence is not conclusive, it appears that the Wagner leader did die in the incident.
John Sawers, who led Britain’s foreign intelligence service, MI6, from 2009 to 2014, told BBC Radio 4’s Today show on Thursday: “You can never fully be certain of the facts in places like Russia,” but it did appear that he was dead.
Wagner chief Prigozhin presumed dead in plane crash - in pictures
Nina Khrushcheva, professor of international affairs at the New School University in New York, told the programme Mr Prigozhin is known to have used doubles.
She said: “So it’s not clear if it’s Prigozhin or someone registered as Prigozhin.
“Apparently there was a phone found, his phone ... next to the plane crash, but if anybody knows how to evade Putin justice or Putin revenge, probably Prigozhin would know best because they go back years and years.
“And also before, I think in 2019, Prigozhin was already ‘killed’ – and I put it in quotes – in one of the African countries but it turned out not to be.”
Who was responsible?
Mr Markov said on Thursday it was “absolutely clear” that Ukraine was responsible for the presumed death of Mr Prigozhin, the man whose mutiny posed the biggest threat to President Vladimir Putin’s almost quarter-century rule.
Speaking to BBC Radio 4's Today programme, Mr Markov said: "For me it is absolutely clear that Prigozhin has been killed by the Ukrainian intelligence service as some kind of gift to [Ukrainian President Volodymyr] Zelenskyy for the independence day of Ukraine, which they are celebrating today."
However, former MI6 head Mr Sawers said the claim was not credible, saying “all indications point to the fact that Putin has taken him out”.
“He’s reasserted his control,” he added.
Ms Khrushcheva said Mr Putin “likes these big bangs, he likes to show that his enemies, his personal enemies, do not escape”.
“We really have very little information and one of the interesting, or maybe not so interesting things, is that almost nobody doubts that one way or another somehow the Kremlin is involved,” she added.
Tatiana Stanovaya, a senior fellow at the Carnegie Russia Eurasia Centre, said on Telegram that “no matter what caused the plane crash, everyone will see it as an act of vengeance and retribution” by the Kremlin, and “the Kremlin wouldn’t really stand in the way of that”.
“From Putin’s point of view, as well as the security forces and the military – Prigozhin’s death must be a lesson to any potential followers,” Ms Stanovaya said in a Telegram post.
What is the Wagner Group?
Founded by Mr Prigozhin in 2014, Wagner is a private military company which has supported Kremlin objectives overseas, in countries including the Central African Republic, where it has been accused of committing human rights abuses.
At its peak, Wagner had about 50,000 mercenary recruits – many of them ex-inmates recruited directly from prison – fighting in Ukraine.
The US designated the group as a transnational criminal organisation earlier this year, and Wagner has been sanctioned by Australia, Canada, Japan, the UK and the European Union. The UK is on the cusp of proscribing the group as a terrorist organisation, according to reports.
Wagner has a murky legal status, and mercenaries are technically illegal in Russia. The group operates independently of the nation’s official armed forces, and had recently sought to rebuff Moscow’s demands that its recruits sign formal contracts with the military.
The issue was a driving force behind the mutiny, which was directed at Russia’s military leaders rather than Mr Putin himself.
Why would Mr Putin want him dead?
The rebellion, led by Mr Prigozhin, represented the biggest threat to Mr Putin’s rule since he took power.
In the revolt that started on June 23 and lasted less than 24 hours, Mr Prigozhin’s mercenaries swept through the southern Russian city of Rostov-on-Don and captured the military headquarters there without firing a shot, before driving to within about 200km of Moscow in what Mr Prigozhin called a "march of justice” to oust the top military leaders who demanded that the mercenaries sign contracts with the Defence Ministry.
They downed several military aircraft, killing more than a dozen Russian pilots.
Mr Putin first denounced the rebellion as treason and a “stab in the back” and vowed to punish its perpetrators, but hours later made a deal that ended to the mutiny in exchange for an amnesty for Mr Prigozhin and his mercenaries and permission for them to move to Belarus.
Details of the deal are murky, but Mr Prigozhin has reportedly shuttled between Moscow, St Petersburg, Belarus and Africa where his mercenaries have continued their activities despite the rebellion. He was quickly given back lorryloads of cash, gold bars and other items that police seized on the day of the rebellion.
Earlier this week, the mercenary chief published his first video since the mutiny, declaring that he was speaking from an undisclosed location in Africa where Wagner is “making Russia even greater on all continents, and Africa even more free”.
Mr Prigozhin's overseas activities was envied by Russia's military leadership, who have sought to replace Wagner with Russian military personnel in Africa.