Post-election violence has claimed 173 lives in Ivory Coast, the UN says, as international pressure mounts for Laurent Gbagbo to quit the presidency.
The US says it is exploring ways to strengthen the UN presence in Ivory Coast, where Mr Gbagbo's forces are in a tense stand-off with supporters of his rival, Alassane Ouattara.
Liberian mercenaries are helping Mr Gbagbo's troops, the UN has confirmed.
The UN's rights council ordered an official inquiry into the violence.
After a special meeting in Geneva, the council issued a statement condemning violations including "abductions, enforced or involuntary disappearances, arbitrary detentions, extrajudicial, summary or arbitrary executions, acts of sexual violence, denial of right to peaceful assembly, the loss of lives and the acts of destruction of property".
The BBC's Imogen Foulkes in Geneva says the commission's unanimous stand will increase pressure on Mr Gbagbo to step down and for the UN to remain in Ivory Coast.
The UN and world powers have recognised Mr Ouattara as the new president.
Mr Ouattara's supporters have called on the International Criminal Court to prosecute any crimes committed by Mr Gbagbo's associates.
Mr Ouattara and his supporters are holed up in the Golf Hotel in Abidjan, protected by 800 UN peacekeepers.
A US government specialist on Africa told the BBC's World Today programme that various options for defusing the crisis were being considered, and "we're really trying to avoid violence if at all possible".
Senior US official William Fitzgerald said the fact that African countries had called for the special UN human rights meeting was "pretty telling about how unified the Africans are and the pressure that this will continue to put on President Gbagbo - or former President Gbagbo, I should say".
Mr Gbagbo says the vote on 28 November, meant to unify a country split by war in 2002, was rigged in rebel areas that backed Mr Ouattara.
The country's Independent Electoral Commission ruled that Mr Ouattara had won, a decision later certified by the UN. The country's Constitutional Council said Mr Gbagbo had been elected, citing vote-rigging in some areas.
France, the former colonial power, says its 15,000 nationals should leave the country as a "precaution".
The UN has a 9,000-strong peacekeeping force in Ivory Coast, called Unoci, and its mandate has been extended for another six months.
The West African regional grouping Ecowas will hold a special summit in Nigeria's capital Abuja on Friday to consider how to remove Mr Gbagbo from power, Mr Fitzgerald said.
Ecowas sent Nigerian-led forces to help bring peace to Liberia and Sierra Leone in the 1990s.
The Ivorian election, delayed for five years, was supposed to reunite the world's largest cocoa producer, which was split between the government-controlled south and rebel-controlled north in the 2002 conflict.
Former rebel commander Guillaume Soro has been appointed prime minister by Mr Ouattara.
Mr Soro called for the international community to use force to oust Mr Gbagbo.
"The Ivorians cannot engage in talks with a dictator," he said.