So far, the death toll is lower than feared, given Kenya’s history of electoral violence.
In 2007, elections that were viewed as widely flawed touched off bloodshed that left at least 1,300 people dead and 600,000 displaced. After elections in 2013, when voting systems were afflicted by widespread malfunctions and there were again accusations of vote rigging, more than 300 people were killed. Mr. Odinga claimed that he was robbed of victory in both elections.
Many supporters of Mr. Odinga said they were angry that international observers, including former Secretary of State John Kerry, did not appear to take the opposition’s claims seriously.
The protests have also put attention on response by the police. Human Rights Watch called on the Kenyan authorities to exercise restraint.
They “should not use tear gas or live ammunition simply because they consider a gathering unlawful,” said Otsieno Namwaya, Africa researcher at Human Rights Watch.
At the Jaramogi Oginga Odinga Hospital, named after Mr. Odinga’s father, an independence hero, six people were being treated for gunshot wounds and other injuries.
David Okoth, 32, was shot in the neck. His brother, Martin, said the pair had been eating at home when they heard a commotion. When they stepped outside, he said, “we saw a police car coming close by, spraying bullets at us.” One of the bullets hit Mr. Okoth, he said.
Moses Oduor, 28, had traveled to Kisumu from Nairobi to vote in his ancestral home. When young men started rioting, police officials began raiding houses in parts of Kisumu, yanking people outside and beating them, he said.
Mr. Oduor said he sustained broken ribs and a broken leg during a confrontation with police officers. The police also took his wallet, money and phone, he said. “But they threw my ID card back at me,” he said.
Jebel Ngere, a police official overseeing operations in Nyandala, a neighborhood in Kisumu, declined to comment on witnesses’ claims, but he said that many of the protesters were using the election as a pretext to loot. One local supermarket was vandalized, he said.
Protesters, armed with rocks, slingshots and machetes, were being pushed away from major roads and central parts of the city, which the police and soldiers were trying to secure, Mr. Ngere said.
But the protesters kept returning in waves, he said, taunting the police with rocks and other projectiles, before being forced to retreat again.
About 600 uniformed members of the security forces and plainclothes officers have been deployed in Kisumu, a number far greater than after previous elections, according to officials.
On one road in Nyandala, only soldiers and police officers were visible. Some were taking a break, reading newspapers. Others drank fizzy drinks at a shop, the only one open.
Suddenly, a rock was thrown at them from inside a maze of houses. Then another. Two police officials quickly took cover near some stalls and moved along the walls.
“It’s a cat-and-mouse game,” Mr. Ngere said. “But this time around, we have made proper arrangements.”
“Everything is prepared,” he said, in a somewhat ominous tone.