A court in Algiers Wednesday sentenced Karim Tabbou, a key figure in Algeria's anti-government protest movement, to six months in prison for "undermining national unity", one of his lawyers said.

Tabbou, who heads the small, unregistered opposition party UDS, has been detained since September.

The prosecutor last week had requested four years in prison for the 46-year-old, who has denied all charges against him.

Salah Abderahmane, one of Tabbou's lawyers, said an Algiers court Wednesday sentenced him for "undermining national unity".

He was also handed a six-month suspended sentence.

Said Salhi, deputy head of the Algerian League for the Defence of Human Rights (LADDH), said Tabbou would be released on March 26 due to time already served.

He said the conviction was part of a "hardening of justice" and described the verdict as "heavy".

From 2007 to 2011, Tabbou was the secretary of Algerian opposition party the Socialist Forces Front (FFS).

He became a popular figure in the protest movement and his portrait is often brandished at demonstrations.

Different case, similar charge

Also on Wednesday, a court in Mascara, northwest Algeria, tried protest figure Hadj Ghermoul on appeal.

The prosecutor has requested Ghermoul's 18-month prison sentence be increased for spreading videos "harming the national interest", the CNLD prisoners' rights group wrote on its Facebook page.

A verdict is expected on March 25.

Rights groups say several dozen people connected with the protest movement remain in detention, though the exact number is difficult to establish due to rearrests.

Mass protests erupted in Algeria in February last year after then-President Abdelaziz Bouteflika announced a bid for a fifth term after 20 years in power, despite being debilitated by a 2013 stroke.

Less than six weeks later, Bouteflika stepped down after losing the support of the then-army chief in the face of massive weekly demonstrations.

Weekly protests have continued despite Bouteflika's exit and the election of a new president in December.