MOSCOW — A prominent Russian opposition leader faces his third investigation in five months as authorities intensify pressure on the opposition.

The Investigative Committee said today it launched a new probe against Alexei Navalny, who was already charged with theft and with fraud and money laundering in two separate cases.

Investigators now say they also suspect Navalny of defrauding the Union of the Right Forces, a now defunct liberal party, of $3.2 million in 2007.

Navalny, a charismatic 36-year-old lawyer, made his name exposing corruption in state-controlled companies. Last winter, he spearheaded a series of street rallies in Moscow that drew up to 100,000 people before March’s vote that handed Putin a third presidential term.