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By Andrew Cawthorne and Tim Cocks
NAIROBI, Jan 16 (Reuters) - Kenyan police used batons and tear gas to break up protests on Wednesday as the opposition defied a ban on rallies against President Mwai Kibaki's disputed re-election.
In the coastal town of Mombasa and the western opposition stronghold of Kisumu, crowds gathered to protest, some burning tyres, building roadblocks and singing anti-Kibaki slogans.
Police fired gas at and beat about 100 youths in Mombasa, scattering them briefly before they attempted to regroup, witnesses said. In Kisumu, they fired over heads and also used tear gas to disperse gangs of protesters, local media said.
Several hundred protesters also began gathering to march from Nairobi's Kibera slum, Reuters witnesses said.
As many Kenyans and expatriates stayed in their homes, shopkeepers nailed up windows in anticipation of trouble, and traffic was thin in the centre of Nairobi.
Police have outlawed the rallies, which the Opposition Democratic Movement (ODM) has called for three days.
More than 600 people have died and 250,000 been left homeless in the turmoil since Kibaki was sworn in after a Dec. 27 vote that ODM leader Raila Odinga says was rigged.
"Our president Raila says we are going to demonstrate for three consecutive days, and that is what we are preparing to do, whatever the cost," protester Emmanuel Omondo said, in front of dozens of youths around burning tyres in a Kisumu outskirt.
Kenya's political crisis has caused a wave of violence, jeopardised its democratic credentials, angered donors, driven tourists away and hurt one of Africa's most promising economies.
Fuelling doubt over Kibaki's win -- officially by 230,000 of 10 million votes cast -- a senior U.S. official said on Wednesday it was impossible to know who won the presidency.
"We have done our own analysis. What it shows is that the result was extremely close and that whoever won probably won with no more than 100,000 votes at the most," Washington's ambassador to Kenya, Michael Ranneberger, told the Daily Nation.
"It is really not possible to say with certainty who won because the process was not transparent." But he called for power-sharing rather than a fresh vote or re-count.
Since declaring Kibaki the winner on Dec. 30, the head of Kenya's electoral board, Samuel Kivuiti, has also told media he does not know who won the election.
GOVERNMENT CHALLENGES CRITICS
Though Kibaki has solidified his position by naming a core cabinet and convening parliament, the opposition received a boost when their candidate won the post of speaker in the assembly late on Tuesday.
Western powers and Kenya's east African neighbours have complained of irregularities in the presidential vote count.
In a statement, 13 nations, including the United States, threatened to withdraw direct aid to the government, and channel funds via other means, if its commitment to "good governance, democracy, the rule of law and human rights weakens".
But the government challenged critics to provide proof.
"You have publicly claimed that the presidential results were flawed. Can you provide tangible evidence?" said a state advert in local media. "Are you aware that your opinions have created tension? ... We are still waiting!"
The opposition also stands accused of rigging and ballot-stuffing in its own heartlands on Dec. 27.
In a blow to prospects for ending the political deadlock, former U.N. chief Kofi Annan, who was expected to start mediation on Wednesday, delayed his mission due to illness.
Police chiefs said they would not allow a repeat of violent scenes during previous opposition protests. Past rioting and looting have wrecked Kisumu, while Nairobi saw a day of running street-battles right into the city-centre.
"We are ready to quell demonstrations," Grace Kaindi, head of the western Nyanza region including Kisumu, told Reuters.
In Mombasa, protesters, who sang songs and blocked one of the main highways, accused authorities of using excessive force.
"They are beating us up and using teargas against innocent people," said Khalid Hussein, of the local Muslims For Human Rights group. "Let them kill us but we will not stop." (Additional reporting by Helen Nyambura-Mwaura, Joseph Sudah, Nick Tattersall, Celestine Achieng, Noor Khamis in Nairobi; Guled Mohamed in Kisumu; editing by Keith Weir)
A bicycle taxi operator cycles past a bonfire in the western town of Kisumu January 16, 2008. Youths erected roadblocks, shopkeepers nailed up windows and Kenyan riot police guarded streets before ...
