Roughly 400 mercenaries are operating in Kyiv under Kremlin orders to assassinate Ukraine president Volodymyr Zelensky, it has been reported.
Armed militia from the Wagner Group were flown into the capital from Africa five weeks ago, it's claimed.
The militia have been ordered to decapitate Zelensky’s government in return for a handsome financial bonus.
The scheme is part of Vladimir Putin's plan to try and seize Kiev, knockout the government and conquer Ukraine within 48 hours - a plan that has so far failed.
The Ukrainian government got wind of the mission on Saturday morning, reports The Times, and mere hours later Kyiv declared a 36-hour 'hard' curfew to sweep the city of saboteurs.
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Civilians were warned they risked being 'liquidated' if they stepped outside.
The Times reports that a source close to The Wagner Group, which is run by one of Putin's closest friends, said between 2,000 and 4,000 mercenaries are operating across the whole Ukraine with the 400 in the capital having slid into Kyiv via Belarus.
It is hoped that peace talks, set to get underway today, may begin to de-escalate the war although there are also fears Belarus could soon send troops into Ukraine, backing their long-time ally Russia.
But it is not known how serious Russia are about the talks or what their demands will be five days after invading Ukraine following weeks of troop build up along the border.
The Wagner Group mercenaries are in contact with the Kremlin are awaiting a signal before unleashing bloodshed on the streets, The Times says, with a hitlist that contains Zelensky and 23 other figures including the prime minister, the cabinet, the mayor of Kyiv, Vitali Klitschko and his brother Wladimir, both popular former boxing champions.
After Moscow invaded last week, Zelensky addressed the nation, claiming that Russian special forces were in the capital searching for him as “target No 1”.
However when he was offered the chance to flee by America he said: “I need ammunition, not a ride.”
Boris Johnson has said Britain will do all it can to get more arms to the beleaguered Ukrainian military as Russian forces continue to threaten Kyiv.
The Prime Minister spoke again on Sunday evening to President Zelensky who told him the next 24 hours would a "crucial period" for his country.
Russian and Ukrainian forces have again been engaged in heavy fighting ahead of the widely expected assault on the capital.
Earlier, Mr Johnson dismissed a dramatic announcement by Vladimir Putin that he was putting Russia's nuclear forces on heightened alert as a "distraction" from the failure of his troops to breakthrough in Ukraine.
President Putin sent shock waves through Western capitals with his instruction on Sunday to his top military leaders to put the strategic nuclear deterrent on a "special regime of combat duty".
The US said it was "completely unacceptable" while a senior US defence official was quoted as warning the Russian leader had made any "miscalculation ... much, much more dangerous".
