Kenyan police killed at least 30 people in the capital, Nairobi, after the opposition protested against the disputed presidential election in August, two leading human rights organisations have said.
In a new report, Amnesty International and Human Rights Watch (HRW) said police were "directly implicated", while there were unconfirmed reports that they killed another 17 people in the city.
They accused the police of raising tensions by using heavy force in areas they regarded as hotspots for potential violence.
The rights groups say excessive force has become a hallmark of police operations in Kenya.
Last week, the main opposition candidate, Raila Odinga, pulled out of the presidential election re-vote scheduled for later this month.
He said he did not believe a fair vote could be held without reforms in the process.
