Ivory Coast's UN-recognised President, Alassane Ouattara, has urged restraint after the dramatic capture of his rival Laurent Gbagbo.
He promised Mr Gbagbo a fair trial and said a truth and reconciliation commission would be set up.
Mr Gbagbo, who surrendered after an assault on his Abidjan residence, said he hoped normal life could resume soon.
He had provoked a crisis by refusing to cede power, insisting he had won November's presidential election.
But forces loyal to Mr Ouattara advanced on his residence on Monday, while French tanks backing the UN peacekeeping mission in the country stood by.
UN Secretary General Ban Ki-moon welcomed the detention of Mr Gbagbo, saying it had brought to an end months of unnecessary conflict, and the UN would support the new government.
US President Barack Obama also welcomed his capture, and called on armed groups in Ivory Coast to lay down their arms to boost the chances of a democratic future.
He added that victims and survivors of violence in the country deserved accountability for the crimes committed against them.
Speaking on his TV channel, a sombre Mr Ouattara appealed to Ivorians to "abstain from all reprisals and violence".
"After more than four months of post-electoral crisis, marked by so many human lives lost, we are finally at the dawn of a new era of hope," he said.
Mr Gbagbo, his wife Simone and his "collaborators" would be investigated by the judicial authorities, Mr Ouattara promised. The personal security of Mr Gbagbo and his family would be guaranteed, he added.
The country had just turned a painful page in its history but better times were on the way, the new president declared.
There have been allegations of atrocities by both pro-Gbagbo and pro-Ouattara forces. The UN has reports of more than 1,000 people being killed and at least 100,000 fleeing the country.
Mr Ouattara called for violence to end and promised investigations into any abuses.
"I call on all my compatriots who are moved by feelings of vengeance to abstain from all reprisals and violence.
"I express my wish to put in place a commission of truth and reconciliation which will shed light on all the massacres, the crimes and other human rights violations."
And he made a direct appeal to all those who took up arms against their countrymen as the presidential dispute dragged on.
"To all those young people who've turned into militia men: they must understand that their fight has no meaning today. I therefore ask them to lay down their arms."
UN peacekeeping chief Alain Le Roy confirmed that Mr Gbagbo and his wife were under UN police guard at Abidjan's Golf Hotel, where Mr Ouattara has his headquarters.
Mr Gbagbo has been shown on pro-Ouattara TV sitting in a room, looking dazed but apparently uninjured, wearing an open shirt and white vest.
The TV channel broadcast a message from the deposed leader in which he called for an end to hostilities.
"I hope that we stop the fighting and get into the civilian part of the crisis, and that we end it quickly so the country can go back to normal," he said.
Forces loyal to Mr Ouattara launched an offensive from their stronghold in the north at the end of March, after months of political deadlock.
As they closed in on Mr Gbagbo's power base in Abidjan, the country's main city, UN and French attack helicopters targeted heavy weapons being used by his forces.
Mr Ban said UN and French forces had acted strictly within the framework of a UN resolution aimed at protecting the civilian population.
He said he wanted to speak to "President Alassane Ouattara" as soon as possible.
"This is an end of a chapter that should never have been," he added. "We have to help them to restore stability, rule of law, and address all humanitarian and security issues."
Mr Le Roy told reporters after addressing the UN Security Council that the chief of Mr Gbagbo's forces had called the UN to say that he wanted to surrender weapons.