Clashes between police and groups of youths broke out in the suburbs of the capital Conakry during the protest against the arrest of members of the National Front for the Defence of the Constitution (FNDC).
The FNDC coalition had been vocal against former president Alpha Conde, who was overthrown in September last year by a military junta.
This week, the demonstrators burned tires, set up barricades, knocked over bins and threw projectiles at the police, who tried to disperse them with tear gas.
The protests were among the first against the administration of military ruler Mamady Doumbouya, who took power after the coup.
On Tuesday police arrested three FNDC leaders: Mamadou Billo Bah, rapper Alpha Midiaou Bah also known as Djanii Alfa, and the coalition's national coordinator Oumar Sylla.
According to prosecutors, Sylla and Bah face charges of having "produced and disseminated... insulting remarks" online against the National Transitional Council (CNT), a legislature appointed by the junta to pass laws pending a declared return to civilian rule.
The rapper, Alfa, had recently criticized comments made by the president of the CNT, before being threatened with arrest by the prosecutor, according to his lawyer.
They were seized during a press conference. Supporters complained that Sylla and Bah were beaten and had their clothes torn by police officers.
The three men were still being detained on Thursday, pending an appearance before a judge.
There has been widespread political condemnation of the arrests, and the methods used.