Three people, including a child, have been shot dead in Kenya in opposition protests which raged overnight into Saturday after the hotly disputed election victory of President Uhuru Kenyatta.

Demonstrations and running battles with police broke out in Nairobi slums after anger in opposition strongholds against an election that losing candidate Raila Odinga claims was massively rigged.

An AFP photographer saw the body of a nine-year-old boy whose family said he had been shot in the back while watching the protests from a fourth floor balcony in Mathare, a slum in the capital.

The violence is a reminder of the bloodshed that followed a disputed 2007 election which led to two months of ethno-political violence that left 1,100 dead and 600,000 displaced.

Attention is now focused on Odinga and his first reaction to Friday’s official election results.

He previously said the loss was a result of massive rigging of Tuesday's polls, which his party denounced as a “charade” and a “disaster.”

Protests erupted in Odinga’s strongholds in western Kisumu county and poor areas of Nairobi almost immediately after the election results were declared Friday, with gunshots ringing out and fires in the streets.

“We have one person killed and four others admitted in hospital with gunshot injuries,” said Dr Ojwang Lusi, the regional health chief in western Kisumu county.

“My brother was shot and yet he was just standing outside our house where people were demonstrating now he has a bullet injury on the hip,” said Truphena Achieng, at a Kisumu hospital.

In the southwestern town of Siaya, a police officer speaking on condition of anonymity, said a man had been shot dead in a demonstration, but “we have not managed to collect the body... because of resistance from protesters.”

The charity Doctor Without Borders (MSF) on its Twitter feed said that 19 people had been wounded in Mathare.

Human Rights Watch on Saturday urged police to show restraint.

Odinga, 72, is a veteran opposition politician seen as having taken his last shot at the presidency, which he has sought four times. He believes elections in 2007, 2013 and now 2017 were snatched away from him.

Politics in Kenya is largely divided along tribal lines, and the winner-takes-all nature of elections has long stoked communal tensions.

Odinga’s ethnic Luo supporters -- and their allies from other groups -- believe they have been denied political power by elites from the Kikuyus, the same ethnic group as Kenyatta, the country's biggest community.

“Amid the anxiety over how the situation would unfold, there was also much joy in Kenyatta's strongholds after he was declared the victor with 54.27 percent to Odinga’s 44.74.

In his acceptance speech Kenyatta urged Odinga and his supporters, to “work together... so that we can build this nation together.”

Foreign observers praised a peaceful, credible voting process -- which saw turnout of 78 percent -- but the mood quickly turned sour when Odinga rejected the results after only a few hours of counting earlier this week.

The main opposition coalition, the National Super Alliance (NASA), has claimed both that the outcome was manipulated by a massive hacking attack, and that it is in possession of results being concealed on IEBC servers that show Odinga to be the rightful winner.

On Thursday, it demanded Odinga be declared president. In 2013, Odinga took his grievances to court and lost.

(Source: Agencies)