UKRAINIAN military intelligence celebrated the killing of former Socialist Party of Ukraine leader Illya Kyva near Moscow on Wednesday.
Kiev warned that a similar fate awaited any another “traitors.”
Mr Kyva fled to Russia shortly after Moscow’s invasion but was found dead with gunshot wounds to the head in the village of Suponevo, just west of the Russian capital Moscow.
Earlier this year, Mr Kyva was given a 14-year jail sentence by Ukrainian authorities for high treason for calling on Kiev to surrender after Russian troops invaded the country in February 2022.
As he had already fled Ukraine he was convicted in absentia.
Since his flight to Moscow, Mr Kyva was a frequent participant in talk shows on Russian state television during which he attacked the Ukrainian leadership.
Mr Kyva’s killing follows a slew of other attacks on critics of the Kiev government.
Lugansk regional parliament deputy Oleg Popov was killed in a car bombing in Ukraine’s eastern Lugansk city on Wednesday, local officials said.
A few weeks ago another Lugansk regional deputy, Mikhail Filiponenko, was killed in a similar attack that was claimed by Kiev.
In August 2022, Darya Dugina, the daughter of Russian nationalist ideologist Alexander Dugin, died in a car bomb explosion outside Moscow.
In April, Vladlen Tatarsky, a prominent Russian military blogger, was killed by a bomb that was planted in a bust depicting him.
In May, Zakhar Prilepin, a Russian nationalist writer who fought in Ukraine, was wounded in a car bombing.
And in October, another former pro-Russian Ukrainian lawmaker who fled the country, Oleg Tsaryov, was shot and wounded in an attack in Crimea.
Spokesman for Ukraine’s military intelligence Andriy Yusov told Ukrainian TV: “Yes, we can confirm Kyva is no more.
“This fate will befall other traitors of Ukraine and puppets of Putin’s regime.”
Russia’s state investigative committee has opened a probe into the killing.