Former U.N. Secretary-General Kofi Annan may walk away from Kenya's peace talks after his security detail discovered his hotel room in Nairobi was bugged, according to a report.

Sources at the Serena Hotel, where the talks are taking place, said Annan's security detail became wary of his safety after discovering that his personal conversations were being intercepted, South Africa's Independent Newspapers reported.

Who may have planted the listening device and how long it was there remain unclear, the Independent reported.

Annan is said to be "livid," but it is not yet known whether he will walk away from the already troubled negotiations.

Click here to read the full Independent Newspapers' report.

Meanwhile, a U.N. fact-finding mission arrived Wednesday in Kenya to assess allegations of grave human rights violations since the country's disputed presidential election, which unleashed weeks of deadly violence.

The three-week mission — sent by the U.N. High Commissioner for Human Rights Louise Arbour — will gather information from the government and the opposition, along with victims and witnesses. The findings will be made public.

"Truth and accountability are of critical importance in putting an end to the violence and preventing future human rights violations," Arbour said in a statement Tuesday from her agency's headquarters in Geneva, Switzerland.

U.N. associate spokesman Farhan Haq, at U.N. headquarters in New York, confirmed that the fact-finding mission had "arrived in Kenya today."

The Dec. 27 election, which foreign and local observers say was rigged, returned President Mwai Kibaki to power for a second five-year term after opposition leader Raila Odinga's lead evaporated overnight.

The ensuing violence has killed more than 1,000 people and has devastated the country's economy.

Violence continued in western Kenya, scene of some of the worst postelection clashes.

Police said they fired to disperse hundreds of residents who had barricaded the gates of the police station in Litein on Tuesday, 145 miles west of Nairobi. Two teachers were killed.

In a forest nearby, officers on Wednesday retrieved 18 bodies with gunshot and machete wounds. They had been killed in four days of clashes between rival gangs which police stopped by throwing grenades.

Aside from clashes with police, much of the fighting has been between rival ethnic groups, with much of the anger aimed at Kibaki's Kikuyu tribe, long resented for dominating politics and the economy.

The violence has been shockingly brutal in a country once considered among the most stable in Africa, with thugs using crude weapons such as machetes and bows and poisoned arrows. The top U.S. diplomat for Africa said last month she saw the violence as ethnic cleansing, but the State Department backed away from her statement, saying the U.S. had not yet concluded whether atrocities had been committed.

Odinga is demanding a new election, but Kibaki has refused, arguing his re-election was fair.

On Wednesday, Odinga's Orange Democratic Movement threatened to organize more mass rallies and stop a gathering of African foreign ministers in Nairobi because they were not consulted about the meeting.

The opposition's previous protests have turned violent, with police firing tear gas and live bullets to break up crowds. "The (threat) of a mass rally stands," said Ahmed Hashi, an ODM spokesman, adding the party "will make sure that they do not meet here."

He did not say when or where the protests would take place or what other measures the party planned.

The opposition is upset at not being consulted over plans for a meeting Thursday of the foreign ministers from an East African bloc known as IGAD, which Kibaki heads.

"This government is an illegitimate one and the arrival of the ministers means recognizing an illegitimate government," Hashi said. "Let them go elsewhere."

Last month, former U.N. Secretary-General Kofi Annan managed to bring together Kibaki and Odinga who agreed to peace talks aimed at breaking the political impasse and ending weeks of postelection violence.

U.S. State Department spokesman Tom Casey said the talks were going forward. "The most important thing for us is that these two parties work together to end the violence and to arrive at the kind of political settlement that they agree to, whether that's a power-sharing arrangement or some other kind of outcome," he said.

On Tuesday, the two sides began discussing deeper political issues, which Annan said would be tough. But progress was possible — "there are no hard-liners in the talks," he told reporters. The talks, which are expected to last two weeks, continued on Wednesday.

But ODM Member of Parliament Franklin Bett told FOXNews.com that Annan's bugging incident has put a damper on the talks.

"The bugging is a demonstration of bad faith. PNU is committed to dillydallying in the hope that the poisoned political atmosphere in the country to return to normalcy. It is a pointer that the Annan-led team will not achieve anything as the government is determined to frustrate him," Bett said.

Word another key negotiator, South African Cyril Ramaphosa, left the country suddenly. It is believed that Kibaki made it be known that they would not trust the South African's intervention.

British High Commissioner Adam Wood warned on Tuesday that following the unexpected departure of Ramaphosa the future of Kenya now hinged on the outcome of the Annan-led mediation talks.

"If the talks collapse, Kenya will be in serious trouble," Mr. Wood warned. He urged both parties to be sincere in their search for peace lest the nation crumbles.

The Associated Press and Juma Kwayera contributed to this report.