The International Criminal Court's chief prosecutor Luis Moreno-Ocampo has arrived in Ivory Coast to investigate the country's post-election violence.
Mr Moreno-Ocampo will meet victims as well as government and opposition representatives during his visit.
About 3,000 people were killed and 500,000 displaced in months of unrest following the November 2010 poll.
Forces loyal to both President Alassane Ouattara, and his rival, Laurent Gbagbo, have been accused of abuses.
Mr Ouattara took power in early May following a five-month stand-off with Mr Gbagbo, who had refused to accept defeat.
Mr Moreno-Ocampo said he "thanked the government for the invitation" to make the visit, after meeting Prime Minister Guillaume Soro on his arrival.
"We'd like to help Cote d'Ivoire to move ahead," he told reporters, adding that "we will be impartial."
Earlier this month, ICC judges gave Mr Moreno Ocampo the go-ahead to undertake an inquiry.
At the time of the decision, they said there was evidence to suggest that troops loyal to both sides had committed war crimes and crimes against humanity.
November's vote was intended to fully reunify the country, split in two after a civil war in 2002.
Ivory Coast - the world's largest cocoa producer - used to be seen as a haven of peace and prosperity in West Africa.
But under the surface, the country has long been deeply divided along ethnic, religious and economic lines.
Mr Gbagbo, who ruled for over a decade, is under house arrest and has been charged with looting, armed robbery, and embezzlement.
He refused to accept defeat in the presidential poll, despite the UN declaring Mr Ouattara - his long-time foe - the winner.