Diene arrived Tuesday in Abidjan, the commercial capital of Ivory Coast, to examine human rights and the fight against impunity in a country still struggling to recover from political violence in 2011.
"It is important that I look into these developments with respect to the protection of the rights of the victims," he said in a statement.
Ivory Coast was pushed to the brink of civil war three years ago after rival claims of victory in presidential elections the previous year. Former Ivorian President Laurent Gbagbo faces war crimes charges at the International Criminal Court, though human rights groups suspect President Alassane Ouattara played a role in the atrocities.
Elections in 2010 were meant to unite a country divided by civil war in 2006. At least 3,000 people were killed during the post-election crisis in 2011.
Diene said he would pay particular focus to chronic impunity, which he said has plagued Ivory Coast for "decades."
Presidential elections are scheduled for next year in Ivory Coast.