Rajh and Margetic failed to announce protest rallies, breached the public peace and violated road safety regulations, Zagreb Police Department spokeswoman Gordana Vulama.
Vulama said that police officers attempted on several occasions today to contact the two in order to serve them with a summons for an interview. Rajh was served with the summons, but did not respond to it, while Margetic could not be found.
The two were arrested in Zagreb's main square on Wednesday evening.
Earlier in the day, the police announced that misdemeanour charges would be filed against Rajh and Margetic for failing to announce a protest rally in the city's main square where about 200 citizens demanded that last Sunday's presidential election be annulled.