Kenya 2017 Re-run: Teenager Killed As Voting Begins
A teenage boy was killed amid clashes between supporters of opposition leader, Raila Odinga and Police officials.
The opposition tried to block access to polling units in Kisumu community which is a stronghold for Odinga.
Observers say voter turn out seems impressive in the ruling party's strongholds while very few people have come out in other provinces.
Mr Kenyatta is seeking a second term while opposition leader, Raila Odinga has pulled out of the contest.
President Uhuru Kenyatta was declared the winner in an August vote, but it is being held again over "irregularities".
The polls opened at 06:00 (03:00 GMT) with tens of thousands of police and other security staff deployed to protect voters and polling stations.
International observers have scaled down their missions for security reasons.
One voter in Nairobi's Mathare slum, taxi driver David Njeru, 26, told the AFP news agency: "It is my duty to vote. Last time the queue was all around the block and I waited six hours to vote, this time the people are few."
After casting his vote in the town of Gatundu, Mr Kenyatta urged people to cast their ballots so the country could move on.
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