The deputy governor of Kherson installed by Moscow, Kirill Stremousov, has been killed, according to Russian state media.
They quoted the regional governor’s press service as saying he died in a car crash.
Kherson, the only Ukrainian regional centre captured by Russian troops after the February invasion, is being targeted by a Ukrainian counter-offensive.
Mr Stremousov, 45, was appointed to his job two months after the Russian invasion of Ukraine.
He was one of the most prominent proponents of the Russian occupation and became known for aggressive statements on social media.
He was wanted for treason by the Ukrainian police.
In recent days, Mr Stremousov had been urging civilians to leave the eastern bank of the Dnipro river in the face of the Ukrainian advance, amid indications that Russian forces may be abandoning the city.
Ukraine accuses Russia of forcibly deporting local residents.