Russian socialite Ksenia Sobchak is to stand in the country’s presidential election in March, when Vladimir Putin is widely expected to run again.
Sobchak conceded she was an unlikely candidate and said she supported opposition leader Alexei Navalny, who is barred from standing.
However he had warned her not to stand and some commentators now predict an opposition split. The Kremlin welcomed her candidacy, saying it was fully constitutional.
Navalny is currently serving a 20-day prison sentence for his role in organising “unsanctioned” protests.
He is banned from the election because of a conviction for fraud which he says was fabricated.