In an escalation of Kenya's deadly election violence, police have fired live ammunition at rioters and used tear gas on vehicles carrying opposition officials.
Nine bodies with gunshot wounds have been brought to the capital's main morgue, while a young girl is among at least 24 people killed by police gunfire since Tuesday's disputed vote in which President Uhuru Kenyatta was declared the victor, according to a watchdog group.
The police have come under scrutiny for what the Kenya National Commission on Human Rights, which monitors government institutions, described as the "unlawful and unacceptable" use of excessive force.
Seventeen of the 24 people shot by police died in Nairobi, the commission said. It cited allegations of police breaking into homes, beating people, threatening them with rape and demanding money.
The watchdog group also lamented "the destruction of private property by both civilians and allegedly by security personnel in the course of their duty".
According to Leonard Katana, a regional police commander, the police have shot and killed two people during riots by opposition supporters on the outskirts of Kisumu, while another five people have been injured by gunfire in in the city.
In Mathare, where Kenyatta's main challenger Raila Odinga has significant support, police opened fire to disperse protesters who blocked roads and set up burning barricades.
One Mathare resident said his nine-year-old daughter was killed by a stray bullet while playing on the third-floor balcony of their home.
Wycliff Mokaya said: "I was watching her play with her friends when she suddenly fell down.
"She was my only hope."
A mortuary official said nine bodies with gunshot wounds were brought to the Nairobi morgue from Mathare.
Police were also seen firing shots into the air and using tear gas on a large opposition convoy as it tried to enter Nairobi's Kibera slum. Witnesses added that police harassed and assaulted at least four journalists who were covering the violence.
The protests began soon after voting started on Tuesday, when Odinga alleged vote-rigging.
The government has accused those challenging security forces of being criminals intent on looting and destroying property.
In Kenyatta's victory speech, the president, whose father was Kenya's first president after independence, said he was extending a "hand of friendship" to the opposition.
Kenyatta won 54% of the vote to nearly 45% for Odinga, but the bitter dispute over the integrity of the election process tempered what many Kenyans had hoped would be a celebration of democracy. The opposition have said the election commission's database was hacked and the results were manipulated against Odinga.
The unrest has exposed divisions in a society in which poverty and government corruption have angered large numbers. Many see Odinga as a voice for their grievances.
Adding to the rift is ethnic loyalty. Kenyatta is widely seen as the representative of the Kikuyu people, the country's largest ethnic group, while Odinga is associated with the Luo group, which has yet to produce a head of state.
But reconciliation efforts and the introduction of a progressive constitution in 2010 have helped to defuse fears of the kind of ethnic-fuelled violence that followed the 2007 election in which more than 1,000 people were killed. Odinga ran unsuccessfully in that election. He also lost the 2013 vote to Kenyatta and took allegations of vote-tampering to Kenya's highest court, which rejected his case.
Recalling its failed legal challenge in 2013, the opposition has said it will not go to court again. It has not directly urged supporters to stage protests, instead telling them to stay safe.
Most of the country has stayed calm since the election results were declared.