Russian authorities have launched a criminal investigation against prominent opposition activist Alexei Navalny over suspected fraud and money laundering.

Officials say Navalny is being investigated over the alleged theft of $1.8 million from one of his companies.

Russian authorities already have another financial case open against Navalny. Investigators said earlier this year they suspect Navalny played a part in a scheme to steal assets from a state timber company — totaling about $500,000 — while he was advising a local governor in 2009.

Navalny has rejected the charges which carry a 10-year prison sentence.