Three people have been killed and at least four shot and wounded in clashes between police and demonstrators in the Kenyan capital, Nairobi.
Nearly half of Kibera's 800,000 residents could lose their homes
The police were deployed in the Kibera slum to stop a political rally for a former leader of the banned Mungiki religious sect, Ndura Waruinge.
Mr Waruinge intends to be a candidate in next year's Kenyan parliamentary elections.
Kibera is Africa's largest slum with 800,000 people living in a square mile.
Residents have little access to running water and other basic services.
Violence between rival gangs has caused several deaths in recent months.
Kibera's MP and prominent opposition leader Raila Odinga has protested against the use of "excessive force" by the police. Mr Waruinge intends to stand against Mr Odinga.
Witnesses said the police opened fire on rioters, but a police commander denied there were any orders to fire live bullets and said they were investigating.
Police said one of the demonstrators had fired at the security forces.