Mauritania's ex-president Mohamed Ould Abdel Aziz on Thursday pleaded not guilty to charges of graft and illegal enrichment, an AFP journalist saw, in a rare corruption trial of a former head of state.

Aziz, who led the country from 2008 to 2019, went on trial in January along with 10 others, accused of abusing his authority to amass an illicit personal fortune.

"These charges are baseless and you have no proof of any of this," he said in court in the capital Nouakchott.

Aziz, a 66-year-old former general, is facing charges of illicit enrichment, abuse of office, influence peddling and money laundering. He has persistently denied any wrongdoing.

His co-accused include two former prime ministers as well as former ministers and businessmen.

"I am the victim of a plot by those I opposed," Aziz said after the court read out the charges against him following a two-week adjournment.

As before, Aziz invoked Mauritania's constitution, which he said forbids trying a president for acts committed in the exercise of his duties.

"Your court has no jurisdiction to try me," he said before the court began hearing witnesses.

A trader's son who came to power in a bloodless coup, Aziz stepped down in 2019 after two terms in which he defused a jihadist insurgency that has swept across other countries in the Sahel.

He was succeeded by his former right-hand man, Mohamed Ould Ghazouani, in the first peaceful transfer of power between elected leaders in the history of a country marked by coups and upheaval.

But relations soured within months of the handover as allegations emerged of financial misconduct.

Aziz is suspected of siphoning off money from state contracts or the sale of real estate, amassing a fortune equivalent to more than $72 million.

Mauritania ranked 130th out of 180 in the 2022 Corruption Perceptions Index by the organisation Transparency International.

Prosecutions of former heads of state are rare in the world, but especially so in Africa. Most former leaders brought to national or international courts are tried for blood crimes rather than corruption.