Kenya is braced for fresh fighting after last month's bitterly disputed elections, as MPs prepare to take up their new seats and opposition leaders for three days of planned protests.

The streets of Nairobi were clogged with traffic as children returned to school for the first time since political and ethnic violence swept the country in the wake of the December 27 vote. Far from being business as usual, tensions were high in the capital as leaders braced for a showdown in parliament, which reconvenes tomorrow.

Kofi Annan, the former United Nations Secretary-General, is also due to arrive today in the latest attempt to find common ground between the two sides. More than 600 people have died in clashes between rival political supporters, ethnic groups and the police. Some 250,000 people have also fled their homes since President Mwai Kibaki was sworn in for a second term on December 30.

Opposition officials insist that his supporters rigged the election after early results showed the main challenger, Raila Odinga, with a narrow lead. International observers concluded that rigging had taken place on both sides and some have said privately that the result went the wrong way.

Now opposition leaders are planning three days of street protests, starting tomorrow, raising the spectre of fresh violence. They also said that they would try to disrupt the first meeting of Kenya's new 222-seat parliament tomorrow, promising to sit on government benches they say are rightfully theirs.

Salim Lone, a spokesman for Mr Odinga, said traffic jams and children returning to school should not be seen as a sign that President Kibaki had weathered the political storm. “There will be no business as usual as long as this crisis is not resolved,” he said.

Kepha Ngito, who runs a community group in Kibera, Africa's biggest slum, said many children there had opted to stay at home. “The situation has been calm,” he said. “At least there has been no violence for a few days but there's still a lot of tension and we are particularly worried about Tuesday and Wednesday.”

Statements issued by American and European officials at the weekend echoed the opposition position and called for compromise.

Jendayi Frazer, the US Assistant Secretary of State, said that the Government must lift restrictions on the media and called on the two sides to work together on electoral and constitutional reform. “In the meantime the United States cannot conduct business as usual in Kenya,” she said.

President Kibaki has tried to maintain the illusion of stability despite a crisis that is being felt all around East Africa. Fuel shortages have been reported in Uganda and Burundi, while the UN is concerned that aid operations from the Democratic Republic of Congo to Somalia are being disrupted by a bottleneck at the port of Mombasa.

Ethnic tensions remain high in areas where gangs of opposition supporters have targeted people they believe voted for the president, such as members of the Kibaki's own Kikuyu tribe. Thousands of tourists, vital to the country's economy, have cancelled safaris or beach holidays.

In the meantime, President Kibaki has ploughed on with establishing his new Government. Last week he named 17 ministers to his Cabinet — prompting another night of violent protests — and has insisted there is no need for international mediation.

John Michuki, Minister for Roads and Public Works and a key ally of the President, said today that Mr Annan had not been invited to Kenya by the Government. “We won the elections so we do not see the point for anyone coming to mediate power-sharing,” he said.

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