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 and world powers have recognised Mr Ouattara as the new president. The UN Human Rights Commission is meeting in Geneva to discuss the crisis. It says 173 people have been killed in the past week and nearly 500 arrested in Ivory Coast. The BBC's Thomas Fessy in the main city, Abidjan, says there are many reports of night raids on neighbourhoods loyal to Mr Ouattara, but Mr Gbagbo's forces are blocking access to those areas and the killings are hard to verify. 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. Divided country A senior 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". US Deputy Assistant Secretary of State 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 in Abidjan, says its 15,000 nationals should leave the country as a "precaution". On Wednesday the World Bank said it had stopped lending to Ivory Coast and had closed its office in Abidjan. The US and EU have imposed travel bans on Mr Gbagbo and his top aides. Neighbours alarmed 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. The 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," Mr Soro said. Source: BBC