UN forces patrol outside the Golf Hotel in Abidjan. The United Nations has said at least 173 people have been killed and dozens of others have gone missing or been tortured following Ivory Coast's disputed presidential election.

Abidjan - Ivory Coast state television disappeared from the airwaves outside the nation's largest city late on Thursday, a blow to the incumbent president's attempts to cling to power in the bloody aftermath of an election most of the world says he lost.

Meanwhile, the United Nations said at least 173 people had died in violence over the November 28 runoff vote and that government forces were blocking access to a possible mass grave. The UN deputy human rights commissioner in Geneva, Kyung-wha Kang, detailed hundreds of arrests and detentions, and dozens of cases of torture and mistreatment.

The state television channel controlled by incumbent Laurent Gbagbo continued to air in Abidjan, but only black and white snow appeared in at least six other cities around the West African nation just minutes before Ivorians sat down to their nightly newscast, residents said.

It was not immediately clear how the signal was cut off. Advisers to Gbagbo's challenger, Alassane Ouattara, refused to comment but the event falls in line with a series of strategies Ouattara has been employing to try to break Gbagbo's stranglehold on the news.

A week ago, Ouattara's supporters unsuccessfully attempted to seize control of the channel. Ouattara has been broadcasting a private radio station that intersperses rally songs with news broadcasts from the Golf Hotel, where he has been holed up since the election. Ouattara also had said that he planned to launch his own version of state TV.

There was no immediate comment late on Thursday from representatives for Gbagbo.

The UN, US, France and others have said Ouattara won the runoff vote, but Gbagbo has refused to step down. State TV ran continuous footage of Gbagbo taking the oath of office in the days after he declared victory without mentioning that his claim was heavily contested.

The UN Human Rights Council adopted a resolution late on Thursday calling for an end to the violence, which has raised fears of a return to civil war. Kyung-wha told diplomats that there may be more fatalities than the ones she was able to document.

“Unfortunately it has been impossible to investigate all the allegations of serious human rights violations, including reports of mass graves, due to restrictions on movement by UN personnel,” Kyung-wha said. “Indeed, the Special Representative of the Secretary-General was stopped at gunpoint as he sought to verify such allegations.”

UN deputy spokesman Farhan Haq said that forces loyal to Gbagbo, supported by masked men armed with rocket launchers, were blocking the road to a village outside Abidjan “where allegations point to the existence of a mass grave.”

Kyung-wha also expressed concern about Ivory Coast media being controlled by political allies of Gbagbo. She said state television and some private newspapers were inciting “hatred and violence” and releasing “false and inflammatory information against the United Nations”.

Amid the rising concerns over violence, the US has said it and other countries are discussing ways to help quell the post-election violence.

State department spokesman PJ Crowley told reporters on Wednesday: “We are in discussions with other regional countries to see if there are ways in which we can reinforce the UN peacekeeping force. It could be that that kind of reinforcement could be another way to send a clear message to President Gbagbo.”

Crowley declined to name the countries that have been contacted but noted that Nigeria is a major troop contributor to West African peacekeeping forces. He also noted that France has interests in Ivory Coast, a former French colony where at least 13 000 French citizens reside.

A Nigerian military spokesman said on Thursday that military intervention into another country could only be decided by the president, and a presidential spokesman could not be reached for comment. The regional bloc Ecowas was due to hold a meeting on the crisis late on Friday.

There has been little international interest so far in a military intervention in Ivory Coast, which suffered a 2002-2003 civil war. The US and the EU are imposing sanctions targeting Gbagbo, his wife and political allies. Hundreds of UN peacekeepers have been protecting the hotel where Ouattara is based.

Over the weekend, Gbagbo ordered all UN peacekeepers out of the country immediately. The UN considers Ouattara president and is staying put, raising fears that UN personnel and other foreigners could be targeted as tensions mount.

Charles Ble Goude, Gbagbo's minister of youth, called for demonstrations next Wednesday. Goude is the subject of a 2006 United Nations sanction for his role in inciting the Young Patriots, a pro-Gbagbo group that led violent attacks against foreigners, especially French citizens.

The US state department has ordered most of its personnel to leave because of the deteriorating security situation and growing anti-Western sentiment. France and Germany also have recommended that their citizens leave.

On Thursday, the UN said at least 471 arrests and detentions had been substantiated from December 16-21. It said at least 90 people had been tortured or treated inhumanely and that there had been 24 disappearances.

The UN also has expressed serious concern about the involvement of foreign mercenaries from neighboring Liberia, which suffered brutal back-to-back civil wars until 2003.

UN peacekeeping chief Alain Le Roy has confirmed that the mission in Ivory Coast “has seen what appear to be mercenaries from Liberia and perhaps Angola”. He said they did not speak any of the local languages in Ivory Coast.

Ivory Coast's 2002-2003 civil war saw the involvement of Liberians fighting on nearly all sides of the conflict. The two countries share a porous, 600km border. Liberia's president has urged citizens not to get involved in Ivory Coast's political crisis.

Ivory Coast was once an economic hub because of its role as the world's top cocoa producer. The 2002-2003 civil war split the country into a rebel-controlled north and a loyalist south. While the country officially reunited in a 2007 peace deal, Ouattara draws his support from the northern half of the country, where he was born, while Gbagbo's power base is in the south.

Gbagbo claimed victory in the presidential election only after his allies threw out half a million ballots from Ouattara strongholds in the north, a move that infuriated residents there who have long felt that they are treated as foreigners in their own country by southerners. - Sapa-AP