NAIROBI, Kenya -- Violent rioting erupted Wednesday as Kenyan opposition leader Raila Odinga alleged fraud in the country's general election, saying hackers had infiltrated the database of the country's election commission and manipulated the results in what he called an "attack on our democracy."

Odinga's allegations followed the release of election results showing President Uhuru Kenyatta with a wide lead over the opposition leader after votes from the vast majority of polling stations had been counted.

"Hackers gained entry into our election database" and "created errors," Odinga said at a news conference. "You can only cheat the people for so long," the opposition leader said. "The 2017 general election was a fraud."

Demonstrators set barricades on fire and shout slogans in Mathare, Kenya, on Aug. 9, 2017. AP

In spite of calls from Odinga for people to remain calm, fears new unrest over the election results quickly came to fruition on Wednesday.

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A police official and a witness said two people were shot dead in Nairobi amid protests over the provisional results. Nairobi police chief Japheth Koome said the two were shot as they took advantage of the protests to try and loot. An Associated Press photographer said one of those killed was shot in the head.

Hundreds of protesters took to the streets in Kisumu, a city in southwestern Kenya that is an Odinga stronghold. Kenyan journalist Fred Ooko said people from the Kondele slum in Kisumu had burned tires and blocked roads on Wednesday. Kisumu, a port city on Lake Victoria, is one of Kenya's largest urban centers. There were reports of police clashing with protesters.

In Mathare, an impoverished area of northeast Nairobi, protesters were seen burning items in the street also and chanting against the election result.

A message posted to the opposition leader's Twitter account claimed his party had its own vote tally showing Odinga with almost 1 million more votes than Kenyatta.

Kenyan anti riot police fire tear gas in Kisumu, Kenya, on Aug. 9, 2017. Reuters

Odinga also ran against Kenyatta in the 2013 vote and unsuccessfully challenged the results in court with allegations of vote-tampering. The longtime opposition figure also ran in the 2007 election, which was followed by violence fueled by ethnic divisions that killed more than 1,000 people.

Earlier Wednesday, Odinga's camp criticized the election commission for releasing data in the presidential race but failing to post information about which constituencies had been counted.

Election officials acknowledged the opposition objection, but defended their actions.

"We believe that by displaying results, we have been doing well to enhance transparency and accountability in the electoral process, consistent with the commitment the commission has made to the Kenya people," said commissioner Consalata Bucha Nkatha Maina, vice chairwoman of the election commission.

A top official in Kenyatta's Jubilee Party said the opposition's criticism of the electoral process was unfounded.

"Once again, we appeal to Kenyans to be calm, once again we want people to look at the figures soberly," said the official, Rafael Tuju. "These results are not coming from out of the blue, but by fact and you cannot claim that results are fake with respect to presidential and you welcome the areas where your governors and your members of parliament have won convincingly. You have to accept the results however they come."

Election Commission chief executive Ezra Chiloba dismissed the allegations of election fraud, telling Kenyan media "all is well" with the vote tally.