After he spoke, Abou Moussa, the interim head of the United Nations peacekeeping mission in the country, set light to a symbolic pile of guns thrown into a pit and covered with wood and straw.
Onlookers cheered, shouting that the country's conflict was now over.
The Ivory Coast descended into civil war in 2002, leading to the country being effectively divided into two between militias from the mainly-Muslim north and the mainly-Christian south.
Attempts to end the conflict faltered until a homegrown peacedeal was signed in 2004 between Gbagbo and Guillaume Soro, the rebel leader.
Gbagbo subsequently named the former rebel chief as his prime minister.
Denis Maho Glofiei, head of the Great West Liberation Front (FLGO), one of the four militia groups, said on Saturday that they were disarming in support of the latest peace efforts.
"We've realised that since the signing of the ... peace deal, we have no more reason to exist. Anyone possessing an arm from today does so illegally and not in the name of the FLGO," he said, after handing a machine gun and rifle to Gbagbo.
Disarming of the pro-government militia groups has long been a major obstacle to peace as the anti-government rebels maintained they would not turn in their own guns until they were gone.