Asked if there were any explanations for the arrest or any formal charges, Teixeira Cândido said that no clarifications had been provided.
The president said the union is preparing a statement on the matter, which it will release shortly.
Initially six journalists had been arrested, but three have since been released.
The attempt at a demonstration organized by young people from civil society, with the support of leaders of the National Union for the Total Independence of Angola (UNITA) -, was thwarted by the authorities, resulting in 103 arrests, police injuries, and demonstrators in numbers undisclosed, in addition to the destruction of means of the forces of order.
The protests were also marked by the throwing of stones, the placing of barricades on the road with garbage containers and tires burning by the protesters.
The march, called by civil society activists, had the support of UNITA and other opposition forces and aimed to demand better living conditions, more employment and the holding of the first municipal elections in Angola.
