The National Commission on Human Rights in Kenya has accused the country's election authorities of serious abuses.
It says the alleged abuses could throw the results of last month's presidential elections into doubt.
Speaking at a news conference, the head of the commission, Maine Kiai, said that in the circumstances, there was no way of knowing the real result.
Meanwhile, Kenya's opposition says it will change tactics to protest against the outcome of the election.
This follows three days of mass rallies.
The Orange Democratic Movement says that from next week it will boycott companies run by allies of President Mwai Kibaki.
At least 14 people have been killed in two days of clashes with Kenyan opposition protestors, with police vowing to crack down on a third day of demonstrations today.
Seven people were killed in the western opposition stronghold of Kisumu and the others died in the capital Nairobi, mainly in volatile slums where hundreds of protestors clashed with police.
One man was killed in ethnic violence when protests spread to an area near the famed Maasai Mara game reserve in the south of the country.
On the last of three days of protests, police said a man from President Kibaki's Kikuyu tribe was shot with an arrow when he ran into a group of Maasai.
Maasai and Kikuyu had been fighting in the Narok area since yesterday with homes and shops burned and at least 23 wounded, the police said.
100,000 children displaced: UNICEF
Meanwhile, the UN has said that more than 100,000 children have been displaced by the recent unrest.
UNICEF says that many have witnessed their homes burnt to the ground and others have seen their loved ones brutally killed.
Some 75,000 children are thought to be living in more than 100 camps for displaced people that have sprung up in churches, police stations and showgrounds since the crisis began.
The agency said that while schools have officially re-opened across the country many fewer children were turning up for class, because they have been displaced or their families are fearing for their lives.
UNICEF said it was setting up classroom tents in several locations, responding to civilians' most immediate needs in sanitation, health and nutrition.
Former UN Secretary-General Kofi Annan has recovered from flu and will travel to Nairobi on Tuesday to help mediate in the political crisis.
In a statement, Mr Annan said the purpose of his mission was to help the Kenyan people find a 'peaceful and just solution' to their post-election crisis.
