NAIROBI, Kenya — The vote count from Kenya's election was rigged, but both parties could have been involved, the chief U.S. envoy for Africa said Monday, declining to blame either President Mwai Kibaki or the opposition leader who ran against him.

The opposition leader, Raila Odinga, canceled nationwide protests, saying Monday he wanted to avoid new violence and give mediation a chance to resolve the election standoff that has killed nearly 500 people in political and ethnic bloodletting.

"Yes, there was rigging," the U.S. envoy, Jendayi Frazer, told The Associated Press. "I mean there were problems with the vote counting process ... both the parties could have rigged."

She said both rival parties could have been involved and that she did not want to blame either Kibaki or Odinga.

Frazer, who has spent three days negotiating with Kibaki and Odinga, said at an earlier news conference that Kenyans "have been cheated by their political leadership and their institutions." In particular, Frazer said, the electoral commission was flawed and needed reform.

The commission chairman has admitted that he is not sure Kibaki won the vote.

Reports of ethnic killings continued to stream in from the countryside, with an official in neighboring Uganda confirming 30 Kenyan refugees were thrown into the border river by attackers, and were presumed drowned.

Two Ugandan truck drivers carrying the group said they were stopped Saturday at a roadblock mounted by militiamen who identified the refugees as members of Kibaki's Kikuyu tribe and threw them into the deep, swift-flowing Kipkaren River, said Himbaza Hashaka, a Ugandan border official.

The drivers said none survived, Hashaka said.

A statement Monday from the Ministry of Special Programs put the death toll at 486 with some 255,000 people displaced from their homes. The toll, which did not include the drownings, was compiled by a committee of humanitarian services set up by the government which toured areas most affected by riots and protests.

Odinga told Sky News television that Kibaki's "rigging" himself back into power caused the violence and therefore "Mr. Mwai Kibaki must bear responsibility ... for the deaths we are seeing in our country today."

But a government spokesman said officials were investigating "premeditated murder" of people warned beforehand that they would pay if they voted for Kibaki.

Such targeting of certain communities "can ultimately result in serious crimes under international law such as crimes against humanity and genocide," said the spokesman, Alfred Mutua.

He did not say who could be charged.

Odinga called off protests planned for Tuesday after meeting with Frazer, who later said that the turmoil had not shaken U.S. confidence in Kenya as a regional hub. Kibaki's government, accused by Odinga of stealing the Dec. 27 election, had said the proposed Tuesday demonstrations were illegal and could provoke violence.

Attempts to hold opposition rallies last week were blocked by police who fired tear gas, water cannons and live bullets over people's heads. Human rights groups accused police of excessive force and unjustified killings in the crisis, but police Commissioner Hussein Ali insisted Sunday that "we have not shot anyone."

For Frazer, Monday was the last day of a three-day mission in which she has won an offer from Kibaki to form a coalition government and a concession from Odinga that he would negotiate without insisting that Kibaki first resign.

The United States, Britain and the European Union have urged Kibaki and Odinga to negotiate. The East African nation is considered an ally in the fight against terrorism.

State Department spokesman Sean McCormack told reporters Monday that Frazer is working with both leaders "to try to get them to open up lines of communication. It's critically important for Kenya and the Kenyan people that these two leaders find a way to bridge whatever differences there are between them."

Meanwhile, thousands of tourists have canceled vacations at the beginning of the high season.

"Hotels have been projecting an occupancy of 80-90 percent of capacity. But today, as we speak, that has dropped down to less than 40 percent. That's a huge loss for the economy," Mohammed Hersi, general manager of Whitesands Hotel in the coastal city of Mombasa, told AP Television News.

Schools were to reopen after the holidays on Monday, but the government postponed that for a week. Many are being used by refugees.

The level of violence eased over the weekend, though ethnic attacks continued, pitting Odinga's Luo and other tribes against Kibaki's Kikuyu people, the largest among Kenya's 42 tribes.

Nearly 1,000 Luos were chased Sunday from their homes in one small town, Limuru, 30 miles west of Nairobi, the capital. Some with furniture and bundles of clothing, others with nothing, they huddled around the compound of the local police station.

George Otieno, 30, said about 100 men armed with machetes, hammers and sticks attacked his home and smashed his head with a hammer.

"They said, 'You have to go back to your place,"' meaning the Luo's native lands in western Kenya, said Otieno, whose head was bandaged and shirt marked with dried blood.

About a mile away, more than 500 Kikuyu refugees were at a Red Cross compound, forced from their homes in the remote Western Province that is a Luo stronghold. Thousands of Kikuyus are fleeing western Kenya under armed police escort.

Francis Waweru said he had arrived three days ago with his wife and four children, fleeing a mob of hundreds who torched his shop and home in Timboroa. He showed a leg wound where he said he was shot with a bow and arrow.

"They said, 'No Raila, no peace,"' Waweru said.

Associated Press writers Elizabeth A. Kennedy, Katharine Houreld, Tom Odula and Malkhadir M. Muhumed in Nairobi, Todd Pitman in Eldoret and Tom Maliti in Mombasa contributed to this report.