Russian investigators asked a court on Wednesday to place under house arrest the man who emerged as a leading opposition figure from a wave of protests in 2011-2012 against President Vladimir Putin.
Putin's critics accuse the Kremlin of stepping up pressure on dissent in recent weeks, with an eye to upheaval in neighboring Ukraine where demonstrations have unseated President Viktor Yanukovich.
Alexei Navalny is currently subject to a five-year suspended sentence on a theft conviction he says was a Kremlin reprisal for his political dissent.
The federal Investigative Committee, which answers to Putin, said in a statement Navalny had violated an order not to leave Moscow while investigations against him continued. He should therefore be confined under house arrest.
Navalny has been jailed until Monday for resisting arrest earlier this week while protesting the conviction of eight activists found guilty of rioting and attacking police at a protest on the eve of Putin's inauguration to a third term.
He was among hundreds of protesters detained on Monday for demonstrating against what they called a “show trial”.