"The just punishment handed down to certain elements of the gang... (amount to) realising an urgent and legitimate claim of the people," Ahmed Gaid Salah said.

Said Bouteflika -- whose brother resigned in the face of mass protests in early April -- was sentenced on Wednesday for "undermining the authority of the army" and "conspiring" against the state.

He was convicted alongside three co-defendants, including two former intelligence chiefs, who all received the same terms after a swift verdict at a military court for crimes committed in the run-up to the ageing president's resignation.

There has been a wave of arrests targeting Abdelaziz Bouteflika's inner circle in recent months, often ostensibly on the grounds of corruption.

But many fear these moves are little more than a high-level purge and a power struggle between still-powerful regime players, rather than a genuine effort to reform the state.

Longtime army chief Gaid Salah himself faces sustained calls to step down from protesters, who continue to mobilise on the streets some six months after the president's forced departure.

Demonstrators demand that all serving figures associated with the Bouteflika era step aside and credible institutions be set up ahead of any elections, but Gaid Salah has repeatedly insisted that a presidential poll must take place before year-end.

Earlier this month, interim president Abdelkader Bensalah set a December 12 date for those elections.

On Sunday, Algeria's main Islamist party, the Movement of Society for Peace, announced it would not compete in that poll.

"The MSP has decided not to field a candidate for the presidential election in December 2019," the party's communications chief Bouabdallah Benadjimia told AFP.