A US citizen known to have fought with pro-Russian separatists in Ukraine between 2014 and 2017 has been killed in Moscow-occupied Donetsk, Russian media reported Friday.

Russia-installed authorities in eastern Ukraine had earlier this month reported the American -- 64-year-old Russell Bentley -- as missing.

"Russell Bentley, known as 'Texas', a real American, truly from Texas, was killed in Donetsk," the head of the pro-Kremlin RT TV channel Margarita Simonyan, said on social media.

"He was fighting for our guys," she said.

Simonyan gave no details on how he died.

The "Vostok" battalion with which he fought confirmed his death, calling for "exemplary punishment for those who killed Russell Bentley", suggesting he did not die in a Ukrainian attack.

Police in Donetsk said on April 8 that Bentley had gone missing after going to help victims of a Ukrainian strike on Donetsk.

On a Telegram channel previously run by him, Bentley's wife Lyudmila has said he had been "abducted" by Russian soldiers from a tank battalion, calling on them to let him go.

The Texan self-declared communist joined pro-Moscow separatists in Ukraine to fight Kyiv in 2014. He had been given Russian nationality.