The United Nations said that at least 50 people have been killed in Ivory Coast's post-election crisis, amid reports of "massive" human rights abuses, and refused to withdraw its peacekeepers.
The UN force's determination to stay threatens to provoke a showdown with strongman Laurent Gbagbo's hardline supporters, but leaders of the world body said it would remain and investigate reports of death squad killings.
UN High Commissioner for Human Rights Navi Pillay expressed concern about "the growing evidence of massive violations of human rights" in the restive West African country since Thursday.
"In the past three days there has been more than 50 people killed, and over 200 injured," she said in a statement issued in Geneva, vowing "to ensure that perpetrators are held accountable for their actions."
Gbagbo ordered the 10,000-strong UN mission to leave on Saturday, accusing it of arming rebels loyal to his rival Alassane Ouattara, but UN Secretary General Ban Ki-moon dismissed the ultimatum and urged him to step down.
Both Gbagbo and Ouattara claim to have won last month's presidential vote but, while the latter has been recognised as the victor by the international community, the incumbent is clinging doggedly on to power.
Tension has reached boiling point in the commercial capital Abidjan, where violence erupted Thursday during a protest march by Ouattara's supporters, and where Gbagbo's armed forces are in an uneasy stand-off with the UN.
"We're going to continue our patrols but we're not seeking confrontation," said Hamadoun Toure of the United Nations Operation in Cote d'Ivoire (UNOCI). "We're increasing our vigilance, and we're ready for anything."
Fear has gripped the dusty little towns scattered on either side of the ceasefire line that has split Ivory Coast into northern and southern armed camps since 2002, and all the talk is war.
Meanwhile, Britain has urged its nationals to leave Ivory Coast, and the US embassy ordered all but emergency staff home for their own safety.
In Geneva, Pillay said the UN mission "has received reports from hundreds of victims and members of their families about the abduction of individuals from their homes, especially at night."
She said witnesses blame "armed individuals in military uniform accompanied by elements of the Defence and Security Forces or militia groups". Ivory Coast's official "Defence and Security Forces" back Gbagbo's rule.
"Abducted persons are reportedly taken by force to illegal places of detention where they are held incommunicado and without charge. Some have been found dead in questionable circumstances," Pillay added.
France also demanded that Gbagbo restrain his forces, and warned that its 900-strong military contingent in Ivory Coast would defend itself if attacked. Canada added its voice to those threatening sanctions.
The UN mission's mandate is due to expire on December 31, but member states are to meet on Monday to discuss its renewal. Ouattara sent a letter to Ban on Sunday urging that the mission continue.
Both sides in the dispute have accused the other of abuses, but in the commercial capital Abidjan the pro-Gbagbo security services clearly have the upper hand in terms of firepower and motivated personnel.
Ivory Coast has been divided between north and south since 2002, when a failed putsch against Gbagbo triggered civil war. UNOCI deployed in 2004 to monitor a ceasefire, and was assigned to oversee last month's elections.
The UN monitors endorsed results from Ivory Coast's electoral commission that gave Ouattara victory in the November 28 run-off, but Gbagbo's allies on the Constitutional Council annulled the result, claiming fraud.
With both men now styling themselves as president, Gbagbo retains control of the southern armed forces, the Abidjan ministries and the cocoa ports that are Ivory Coast's main source of revenue.
Ouattara is backed by former rebel fighters from the north -- known as the New Forces -- but he and his government are holed up in a luxury golf resort in Abidjan, protected by a cordon of UN peacekeepers.
The United Nations, United States, former colonial power France, the African Union and Ivory Coast's West African neighbours in the ECOWAS bloc have all demanded that Gbagbo step aside and allow Ouattara to assume office.
Instead, there is every sign that the regime is hardening its stance.
On Thursday, troops and police fired on pro-Ouattara demonstrators in Abidjan, killing between 11 and 30 people. Opposition newspapers and radio stations have been banned, and the Golf Hotel is surrounded.
Gbagbo's next move is not yet clear, but his most notorious lieutenant -- Minister for Youth Charles Ble Goude -- called on his supporters to be prepared to fight to reassert Ivory Coast's sovereignty.
"Playtime is over," Ble Goude declared on Saturday, an ominous phrase from a man who has been under UN sanctions since 2006 for "acts of violence by street militias, including beatings, rapes and extrajudicial killings".