Two Russian journalists were arrested by their government on “extremism” charges and ordered by courts there on Saturday to remain in custody pending investigation and trial on accusations of working for a group founded by the late Russian opposition politician Alexei Navalny.

Konstantin Gabov and Sergey Karelin both denied the charges for which they will be detained for a minimum of two months before any trials begin. Each faces a minimum of two years in prison and a maximum of six…