Said Bouteflika, widely seen as the real power behind the presidency after his brother suffered a debilitating stroke in 2013, faces allegations of "undermining the authority of the army" and "conspiring" against the state.

Former defence minister Khaled Nezzar has alleged that as protests mounted against the veteran leader in April, Said Bouteflika had considered declaring a state of emergency and firing army chief General Ahmed Gaid Salah.

His detention in May along with General Mohamed Mediene, who headed the all-powerful secret service for 25 years, and fellow ex-spy chief General Athmane Tartag was part of a wave of arrests targeting the ousted president's inner circle.

They were brought before a military court in Blida, south of Algiers, along with the head of The Workers' Party, Louisa Hanoune, according to private television channels Ennahar and El Bilad.

If convicted they could face lengthy prison terms.

Security was tight with police blocking access by vehicles and pedestrians to the court's two entrances, according to an AFP photographer.

Mediene, known as Toufik, headed the all-powerful DRS intelligence agency from its foundation in 1990 up to his fall from grace in 2015.

Tartag, his deputy, succeeded Mediene and when the DRS was dismantled in 2016 he served as Algeria's security coordinator under the supervision of the presidency.

Hanoune, a Trotskyist lawmaker and three-time presidential candidate, was detained in May on charges of involvement in "a plot against the army".

Her lawyers have acknowledged that she took part in a meeting with Said Bouteflika and Mediene in March, a day after Gaid Salah publicly called for the ailing president to step down.

A string of prominent politicians and businessmen have been questioned or detained over alleged graft since Bouteflika resigned in April after two decades in power in the face of mass protests.

Presidential elections have now been set for December 12, but protesters have kept up their demands for political reforms and the removal of the former president's loyalists, including the army chief himself.