Kenyan police fired tear gas to disperse hundreds of young men demanding the release of a former leader of the banned Mungiki sect.
Police in riot gear chased the protesters through Nairobi, the capital, on Wednesday, frightening residents after post-election violence that killed at least 1,000 people and forced 300,000 from their homes.
"We demand the immediate release of Maina Njenga and his cars, which were impounded by the police," a statement from Mungiki members said.
John Maina Njenga, a former leader and founder of the sect, is serving a five-year prison sentence for the possession of an illegal firearm.
Mungiki, which means "multitude" in the Kikuyu tribal language, is notorious for beheadings, and was accused of killing hundreds of people during the post-election violence.
According to local media, Njenga left the sect while in prison, saying he had become a born-again Christian.
The Mungiki began in the 1990s as a quasi-religious organisation and portrays itself as a champion of the poor.
But police say it is a large organised crime operation, which earns money by extorting protection fees from minibus operators or operating as political "muscle for hire".
The sect was banned in 2002 after members armed with knives and clubs killed more than 20 people in a Nairobi slum.