No, until police prove your identity but no more than for 24 hours. That's nonsense. In case of doubt, burden of proof is on policeman's side. He commits a punishable offence (zneužití pravomoci veřejného činitele ~ abuse of public authority) by turning you in without legal reason. And policeman has minimal chance to prevaricate because he must state you CONCRETE reason before turning you in ("you're similar to somebody wanted" is insufficient, "you're similar to Mr XYZ who is wanted on the basis of this concrete arrest warrant" is sufficient).