A Russian court on Thursday rejected an appeal by opposition leader Alexei Navalny for his release from jail, while authorities detained several of his allies and warned social media companies about promoting more protests after tens of thousands rallied across the country last weekend demanding his freedom.

Russian police arrested more than 2,600 people Saturday in nationwide protests demanding the release of opposition leader Alexei Navalny, the Kremlin's most prominent foe, according to a group that counts political detentions.