The Algerian army said on Tuesday it had killed the head of a militant group that beheaded a French tourist after it had pledged allegiance to the Islamic State group.

The body of Abdelmalek Gouri, who claimed responsibility for the beheading of Frenchman Herve Gourdel in September, was identified after an operation in the town of Isser "that allowed us to eliminate three terrorists", the army said.

Nine illegal migrants from Niger were killed in a traffic accident in Algeria Sunday when their bus and a truck collided as they were being repatriated, the APS news agency reported.

The mayor of a town in Algeria was shot dead and had his throat slit by unidentified "terrorists" on Friday, police were quoted by the APS news agency as saying.

France's last remaining hostage, Serge Lazarevic, arrived home Wednesday after three years in the hands of Islamist militants as questions swirled around the terms of his release.

The government has refused to comment on reports that several Al-Qaida prisoners, including those involved in kidnapping Lazarevic in Mali in 2011, were released in exchange for his freedom.

A criminal court in Algeria on Monday cleared a national repatriated by the United States after 12 years at the Guantanamo prison camp of "terror" offenses, his lawyer said.

Ahmed Belbacha, 45, was acquitted by the court in the capital Algiers for lack of proof, Amine Sidhoum told AFP.

Algeria has begun repatriating thousands of illegal workers to Niger in an operation likely to last several months, the Algerian Red Crescent (CRA) said on Monday.

A first group of 318 arrived at a reception centre on Saturday in the main city in southern Algeria, Tamanrasset, Saida Benhabyles of the CRA told Agence France Presse.

Two young men were killed and about 20 other people wounded when Algerians demonstrating against delays in a government projects clashed with police, media said Saturday.

The confrontation took place Friday in the town of Touggourt, where people were protesting delays "in awarding plots, construction and connection to the water supply," APS news agency aid.

Algerian Justice Minister Tayeb Louh said on Wednesday that the army last month killed a jihadist suspected of taking part in the beheading of Frenchman Herve Gourdel.

"One of the suspects was eliminated in October by the army during an anti-terrorist operation," Louh told reporters, citing a probe into the murder of Gourdel.

The North African jihadist group al-Qaida in the Islamic Maghreb released a video Monday purporting to show a French and a Dutch hostage held since November 2011 in the Sahara.

In the video, found on the Internet by the private terrorism watchdog SITE, French national Serge Lazarevic and a man identifying himself as Sjaak Rijke appeal to their governments to negotiate their release.

Algerian President Abdelaziz Bouteflika, 77, who has been plagued by ill health since suffering a mini-stroke last year, left France on Saturday after a two-day stay in hospital.