Protesters came out on to the streets after reports of Kamel Eddine Fekhar's death. AFP Photo

ALGIERS Algeria is to investigate the death in custody of a prominent human rights activist, the country's justice ministry said.

Kamel Eddine Fekhar, a leading advocate for the minorityMozabite community, died on Tuesday while being held in pre-trial detention, with his lawyer accusing judicial authorities of being responsible.

The 54-year-old activist had been on hunger strike since his arrest in late March, his family have said.

Lawyer Salah Dabouz said Fekhar was held in Ghardaia, 480 kilometres (300 miles) south of the capital Algiers for weeks "in inhumane conditions".

Fekhar, a doctor, died at the Blida hospital after being transferred there "in a comatose state".

In a video posted on his Facebook page, Dabouz denounced "this planned death by the judicial authorities of Ghardaia" who he said detained Fekhar without reason.

In a statement issued Wednesday, the Ministry of Justice said it had "instructed the relevant services to carry out an in-depth investigation into the circumstances of the death of Kamel Eddine Fekhar".

Fekhar was first arrested in 2015 during unrest in the M'zab valley, where Ghardaia is the largest city, between the country's Berber-speaking Mozabite minority and Chaamba Arabs.

Rights groups including Amnesty International had called for an investigation into his death.

The NGO said the authorities must also "immediately review their repressive policies and the shameful treatment of activists and protesters", adding that the country must allow for freedom of expression and the right to demonstrate peacefully.

Algeria's League for the Defence of Human Rights and the Front of Socialist Forces, Algeria's oldest opposition group, had both also demanded justice.

In 2016, a British-Algerian journalist died while serving a two-year jail term for "offending" Algeria's president. Mohamed Tamalt's lawyer said he had lapsed into a coma after going on hunger strike. AFP