Police are battling to stop a planned National Super Alliance (Nasa) prayer rally for victims of police brutality at Jacaranda grounds in Embakasi, Nairobi.
The officers in full anti-riot gear on Tuesday threw teargas everywhere, including residential estates, and beat up whoever they came across.
They started by sealing off the venue before unleashing their arsenal on a group of youths who were marching to the grounds.
Nasa supporters later regrouped and blocked roads, making it impossible for motorists to pass.
But even before the running battles started, a close look at the venue indicated that the requiem mass for victims of police brutality, which was to be led by Mr Raila Odinga, was doomed.
On the night before the rally, unknown people ferried and dumped raw sewage on the spot where dais was to be erected.
Nasa has organised a memorial to remember victims of police brutality during the electioneering period.
Mr Odinga, his co-principals Kalonzo Musyoka and Musalia Mudavadi, Siaya Senator James Orengo and other Nasa leaders were expected to address the rally.
The clash between police and Nasa supporters comes after Nairobi County Police Commander Japhet Koome warned the opposition against holding the meeting.
On Sunday, Mr Koome denied knowledge of the Nasa event and, a day later, vowed not to allow it, saying the only major public event that would take place in Nairobi on Tuesday would be President Kenyatta's swearing-in.
But Nasa co-principal Moses Wetang'ula on Monday dismissed Mr Koome's claims.
“We are planning prayers for our supporters who were shot dead during protests. We will also fundraise for the victims’ families so that they can hold a befitting send-off for their loved ones,” Mr Wetang'ula said.
The Jacaranda meeting was a culmination of a series of memorial services held in other parts of the country.
Nasa claims that 54 people have been killed by police between November 17 and 21.
The figure, according to the coalition, includes 18 who were killed on November 17 as police tried to block supporters from accessing Uhuru Park for a public rally.
They were welcoming Mr Odinga from a 10-day US tour.
Mr Odinga, who pulled out of the October 26 repeat presidential election, has vowed not to recognise Mr Uhuru Kenyatta’s presidency despite the Supreme Court upholding the Jubilee leader's 98 percent-of-votes-cast win.
All Nasa leaders turned down President Kenyatta’s swearing-in invitation, with Mr Odinga terming it "a feast" as other Kenyans "mourn".
“We are mourning, and on the other side, Uhuru is preparing a feast, a ceremony. All patriotic Kenyans will be at Jacaranda mourning our people brutally killed by this regime,” said Mr Odinga.
Reported by David Mwere, Samwel Owino, Collins Omulo and Faith Nyamai.