NAIROBI, Kenya (AP) — Kenyans on Friday were hoping to hear the final results within hours of Tuesday's already disputed presidential election, with President Uhuru Kenyatta holding a strong lead in provisional voting results that opposition candidate Raila Odinga claims had been hacked.

Supporters of Odinga have said an unofficial tally shows he won. But Kenyan election officials say only they have the authority to declare the winner, and international election observers say they have seen no signs of interfering with the vote.

Violence broke out this week in some opposition strongholds in parts of the capital, Nairobi, and elsewhere while most of the nation remained calm. At least three people were killed amid clashes with police.

The election is a test of the stability that has made the East African nation of 44 million people a regional economic power.

Odinga, a former prime minister who has run unsuccessfully for president three times before, said hackers infiltrated the commission's computer system and manipulated results against him. The recent torture and killing of Kenya's election official in charge of the electronic voting system also has raised concerns.

Commission chairman Wafula Chebukati has said a hacking attempt was made but it failed. Kenyatta, 55, whose father was Kenya's first president after independence from British colonial rule, has not commented on Odinga's claims.

Election officials have been painstakingly trying to confirm their provisional results showing Kenyatta in the lead with checks of documents from polling stations nationwide.

The election commission has until Aug. 15 to release the final tally.

The U.S. State Department has urged Kenyans to refrain from violence and patiently await the election commission's announcement of the final results.

"Elections should never be an issue of life or death," said Marietje Schaake, the Dutch head of the European Union mission observing the vote.

Odinga lost in a 2007 election that was followed by violence fueled by ethnic tensions that killed more than 1,000 people. He also lost the 2013 vote to Kenyatta and took allegations of vote-tampering to the Supreme Court, which rejected his case.