Mr Gbagbo surrendered after a military assault on his residence in Abidjan.

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".

Mr Gbagbo, his wife Simone and his "collaborators" would be investigated by the judicial authorities, he promised.

The personal security of Mr Gbagbo and his family would be guaranteed, he said.

The country had just turned a painful page in its history, he added, but it was entering a new era of peace and hope.

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.

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.