Ex-president Laurent Gbagbo has left Ivory Coast for The Hague-based International Criminal Court, which is probing alleged crimes committed during post-election violence.
Gbagbo, who was notified of his imminent transfer on Tuesday, less than two weeks before legislative elections, and will be the first former head of state to be surrendered to the ICC.
He left the northern town of Korhogo shortly after 6pm (0500 AEDT), Abidjan prosecutor Simplice Kouadio Koffi said.
A source close to the matter said Gbagbo's plane would fly to Abidjan and then on to the Netherlands where it was expected to arrive overnight in Rotterdam, where he would be handed over to ICC authorities.
One of Gbagbo's lawyers, Jean Gbougnon, earlier said: "The prosecutor has served an international arrest warrant on ... Laurent Gbagbo".
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Last month, ICC judges gave prosecutor Luis Moreno-Ocampo the green light to probe post-election war crimes and crimes against humanity committed by forces loyal to both Gbagbo and new Ivorian President Alassane Ouattara.
In Paris, another lawyer for Gbagbo called the ICC arrest warrant "illegal" and said it would only serve to exacerbate tensions in the west African country right before the elections.
"This decision by the International Criminal Court is illegal and goes against the interests of the country and of national reconciliation," lawyer Lucie Bourthoumieux said.
Ivory Coast's new rulers have been pressing for weeks to have Gbagbo transferred to The Hague, at times making his detention at ICC headquarters a condition for "reconciliation" in the deeply divided country.
The United States said on Tuesday the ex-leader must be held accountable for "impeding the peaceful transition to democracy" in Ivory Coast by refusing to concede defeat in last year's presidential election.
"He now needs to be held accountable for any human rights abuses that he may have carried out," State Department deputy spokesman Mark Toner told reporters in Washington.
"I think any credible, transparent trial that holds him accountable for his actions can certainly be constructive in reconciliation efforts."
In Ivory Coast, Gbagbo had appeared before an investigating magistrate in Korhogo on Monday, Gbougnon said.
The former leader faces charges on home soil for "economic crimes", allegedly committed during the political crisis that left 3000 people dead, after his refusal to accept defeat in November 2010 elections.
Gbagbo was arrested on April 11.
His wife Simone is detained at Odienne in the nation's northwest, while dozens of Gbagbo followers and close military and civilian aides are being held for assault, "violating the authority of the state" or economic crimes.
ICC spokesman Fadi el-Abdallah said the court could not comment on the matter until judges made their decision public.
