Talks between the Kenyan government and opposition failed to reach agreement today, raising fears of a return to the brutal post-election ethnic bloodletting which killed more than 500.

As police used tear-gas to scatter a crowd of female opposition demonstrators marching through the capital Nairobi, the departing African Union (AU) chairman left the country with officials saying that he had "failed to break the deadlock" between the two sides.

However as President John Kufuor of Ghana headed back home, it was announced he would be replaced as mediator by Kofi Annan, the former United Nations Secretary General, as both sides in the dispute expressed a willingness to keep on talking.

British tourists to Kenya, meanwhile, faced further disruption to their plans with a ban on charter flights to the strife-torn country extended to at least next Monday. The Foreign Office continues to warn against all but essential travel to the country.

Kenya erupted into a round of brutal bloodletting after the country's December 27 elections led to a disputed victory by President Mwai Kibaki. Raila Odinga, the opposition leader who had been widely tipped to win the poll, accused his rival of rigging the election and the subsequent horrific ethnic violence led to hundreds of deaths.

Human rights groups accused tribal groups affiliated to both parties of ethnic cleansing.

Speaking after Mr Kufuor left the talks, an official told the AFP news agency: "The president of Ghana failed to end the deadlock. Both sides did not let go of their positions."

However Mr Kufuor, speaking himself at the airport in Nairobi, said that the two sides agreed to continue talking despite the apparent deadlock. "Both sides agree that there should be an end to violence," he said.

Earlier, the tension on the streets increased when allies of Mr Kibaki were sworn in as Cabinet ministers, dampening hopes of a power-sharing compromise as talks continued.

In Nairobi, protesters from the women’s wing of Mr Odinga’s party marched in protest chanting "No peace, no justice! Kibaki is a thief." Police fired tear gas at them, claiming they were flouting a ban on demonstrations imposed since the violence erupted. The women were seen running from the scene.

"We are calling for truth about what happened to our votes and the votes of Kenyans," the chairman of the party’s women’s league, Jacqueline Oduol, said.

Rob Crilly of The Times, in Nairobi, said that with no resolution to the dispute over the election the situation remained tense.

"In many ways, it depends on which group wants to press the button," he said. "At the moment things are generally calm, but everyone's holding their breath to see what happens next."

Despite the disputed election results, Mr Kibaki said in a speech yesterday that he considered questions about the vote and the count were "finished, and anybody who thinks they can turn it around should know that it’s not possible and it will never be possible".

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