Kenyan police on Monday fired teargas and a water cannon at stone-throwing supporters of opposition leader Raila Odinga during the second consecutive week of protests against the government and high food prices.
The clashes broke out as Odinga's convoy passed through a neighbourhood in the capital and some supporters threw stones at the police, a Reuters witness said.
Hundreds of supporters had gathered around the convoy in the Kawangware neighbourhood, shouting "Ruto must go," in reference to President William Ruto.
In a Twitter post, Odinga, 78, said Monday's protests would proceed despite a police ban and also reiterated his call for rallies on Thursday.
Odinga has called for the twice-weekly protests indefinitely, citing the high cost of staples such as maize flour, which has kept inflation high. He also accuses Ruto of cheating in last year's presidential election.
Ruto said last week that the protests were hurting businesses and ordinary people.
Odinga, a former prime minister, has lost five elections in a row in his bid to be the president. He challenged the most recent result before the Supreme Court, which upheld Ruto's victory.
In Nairobi's Mathare slums and in the western city of Kisumu, close to where Odinga has his ancestral home, police officers clad in riot gear used tear gas to scatter groups of protesters who were hurling stones at them, footage on Kenyan television station NTV showed.
A Reuters witness reported little activity in Nairobi's central business district, with many shops remaining closed. The district had a heavy police presence ahead of Monday's planned gatherings.
Kenya's police chief on Sunday announced a ban on the protests called by Odinga, saying such acts remained illegal.
On Monday, the Police Reforms Working Group, a coalition of 18 rights groups, asked both the police and the protest organisers to ensure the protests were orderly.
During last week's protests a university student was killed when police fired live rounds after running out of tear gas canisters and blank rounds, according to an internal police report shown to Reuters by a police source.
A police spokesperson did not respond to a request for comment about the report.
Following those protests, police arrested more than 200 people, including lawmakers belonging to Odinga's faction in both houses of the parliament.