In a Twitter post, Odinga said the protests would proceed despite a police ban and also reiterated his call for rallies on Thursday. Nairobi’s central business district had a heavy police presence ahead of Monday’s planned gatherings.

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 unleashed 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.

Kenya’s police chief on Sunday announced a ban on the fresh protests called by Odinga, saying such acts remained illegal.

“We have been restraining ourselves. We cannot do that any more. We are ready as the police force to maintain peace,” Inspector General of Police Japhet Koome told reporters at a media briefing.

On Monday, the Police Reforms Working Group, a coalition of 18 rights groups, asked both the police and the protest organisers to ensure the rallies were orderly.

During last week’s protests police used tear gas and water cannons with Odinga’s convoy among the targets.

A university student was killed last week when the 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.

Police arrested more than 200 people, including lawmakers belonging to Odinga’s faction in both houses of the parliament.

Odinga, 78, 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.

By Humphrey Malalo and Ayenat Mersie

(Reporting by Humphrey Malalo and Ayenat Mersie; writing by Bhargav Acharya and George Obulutsa; editing by Frank Jack Daniel, James Macharia Chege and Mark Heinrich)