Opposition party UNITA said Queiros Chiluvia, a deputy editor at Radio Despertar, was detained on Sunday after entering the Cacuaco police station in the outskirts of Luanda to obtain a reaction about screams coming from prisoners.
UNITA lost a 27-year civil war against President Jose Eduardo dos Santos' MPLA party in 2002 and has since suffered heavy defeats in two elections.
Opposition parties and international rights groups have long accused Dos Santos, who has been in power in Africa's No. 2 oil producer for 34 years, of suppressing freedoms, including those of the press.
"Chiluvia has been charged with invasion, slander and defamation against public authority," UNITA said in a statement.
An Angolan police spokesman was not immediately available for comment.