Navalny, an anti-corruption blogger who has organized protests in the past 12 months against President Vladimir Putin, already faces charges of theft that he says are politically motivated and part of a Kremlin clampdown on dissent.

The federal investigative committee, a government agency, said on its website that Navalny and his brother were being investigated over the alleged theft of $1.79 million by a trading company they are involved in.

It announced the investigation one day before the opposition plans a new march against Putin in Moscow.

Navalny was not immediately available for comment. He has denied the earlier charges, over the alleged theft of timber from a state company in the Kirov region when he was advising the governor there in 2009.

Navalny is threatened with 10 years in jail if found guilty of the earlier charges.