Prosecutors at the International Criminal Court (ICC) said "grave errors" were made in acquittal last year of former Ivory Coast president Laurent Gbagbo, as they began their bid to overturn the decision at an appeals hearing on Monday.
The ICC, the world’s first permanent war crimes court, said in January last year that prosecutors had failed to prove any case against Gbagbo.
Prosecutors at the Hague-based court in the Netherlands have appealed the decision mainly on procedural grounds, arguing that there were legal faults with the way the decision was announced and the way evidence was assessed.
They have said they will seek a re-trial for Gbagbo on charges of crimes against humanity for his role in post-election violence in Ivory Coast in 2010-2011.
Monday's hearing was streamed online as the ICC is closed due to measures aimed at curbing the spread of the novel coronavirus.
The 75-year-old former president, who is living in Belgium on conditional release after spending more than seven years in custody in The Hague, joined Monday's hearing via video link.