Moscow's Basmanny Court has extended the house arrest of opposition leader Sergei Udaltsov until August 6.
The court said April 1 that more time was needed to investigate who organized antigovernment riots in Moscow's Bolotnaya Square in May 2012.
Udaltsov and opposition activists Konstantin Lebedev and Leonid Razvozzhayev have been charged in the case.
All three deny the charges.
Investigators have said the three had "numerous meetings" last year with foreign citizens while planning the violent protest.
Udaltsov's house arrest was first ordered in early February and was set to end on April 6.
The court ruled Udaltsov would not be able to have contact with anyone except members of his family, his attorneys, investigators, and law-enforcement representatives.
Udaltsov was also prohibited from using the telephone and the Internet as well as from sending or receiving letters.
Based on reporting by ITAR-TASS and Rapsinews.ru