Kenya's defeated opposition faced mounting calls at home and abroad to calm their supporters Sunday after claims of election rigging sparked violent protests that left at least 16 people dead.

Odinga's flashpoint strongholds in western Kisumu and Nairobi's slums were quiet Sunday, with signs life was returning to normal after two days of running battles with police, who in some cases fired live ammunition to disperse protesters.

But UN Secretary General Antonio Guterres urged thwarted presidential candidate Raila Odinga to "send a clear message to his supporters urging them to refrain from violence", a message echoed by British Foreign Secretary Boris Johnson.

The anger erupted on Friday night after President Uhuru Kenyatta was declared the victor by a large margin over Odinga following an election pollsters had described as too close to call.

Odinga's National Super Alliance (NASA) coalition has insisted their candidate is the rightful winner, saying he was robbed of victory through hacking and manipulation of an electronic vote tallying system.

However calls for them to take their grievances to court, while Kenya's foreign partners heap congratulations on Kenyatta, have left them isolated and under mounting pressure.

Odinga, 72, a mainstay of the Kenyan opposition since the 1980s, has been silent since his loss was announced, but was due to address supporters in Nairobi's Kibera slum on Sunday afternoon.

His party officials have said they will neither back down nor take their grievances to court, as they did in 2013 when Odinga also cried foul over his loss.

"We will not be cowed, we will not relent," NASA official Johnson Muthama told reporters on Saturday.

In Nairobi's Mathare slum, shops and markets slowly began opening and there was no sign of police or protesters on Sunday.

"We want to hear Raila. We want to hear what he has to say. It's him who will guide us. If he tells us to go on the streets, we will go on the streets. If he wants us to stay home, we will stay stay home," said 25-year-old hairdresser Humpfrey Songole in Mathare.

- 'Exercise restraint' -

According to an AFP tally, 16 people have died since the result was announced Friday.

Seven of those were in the west, which was also calm Sunday morning.

"We have three bodies that were taken to the main mortuary in Kisumu, we also have one in Homa Bay, and there's one in Migori and two in Siaya," a senior police officer said on condition of anonymity, as he is not permitted to speak to the media.

"These are people killed in the confrontations with officers since Friday night," said the officer.

Newly elected Kisumu governor Anyang' Nyong'o -- father of actress Lupita Nyong'o -- urged police to withdraw and allow people to peacefully protest the "stolen election".

Nine people have died in the capital, including a young girl whose family said she had been shot in the back while playing on a balcony in Mathare as police opened fire on protesters.

The Doctors without Borders (MSF) charity said on Twitter that it had treated 54 wounded people in its clinics.

The post-election violence is the worst since a disputed 2007 poll which Odinga claimed was stolen from him. That led to two months of protests and ethnic killings which left 1,100 dead and 600,000 displaced.

Britain's Johnson called on Kenya's opposition to "exercise restraint" to ensure calm.

The European Union's foreign affairs chief Federica Mogherini urged the opposition "to respect the results and to use legal means available for appeals and complaints."

In another blow to the opposition, local election observer group ELOG, which deployed 8,300 observers and conducted a parallel tallying operation, determined Kenyatta had won with 54 percent -- the same figure given by the electoral commission.

- 'Zero-sum game'-

Kenyan media also urged Odinga to address his base.

"NASA must direct its supporters to stand down, no matter how justified it feels that the presidential tally was rigged," wrote the Standard newspaper in an editorial, while slamming the police response to protests.

Interior Minister Fred Matiangi denied that police had fired on "innocent protesters", saying officers had clamped down on "criminal elements" taking advantage of the tension to loot and rob.

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.

"The reason elections have become a trigger for violence is the relationship between power and prosperity. It is a zero-sum game and winning becomes a life and death matter, hence losing is not an option," wrote the Daily Nation in its editorial.

Source: AFP