See what happen's in Kenya election: Long lines as voters wait to cast ballots

Kenyatta, the son of Kenya's founding president and the country's youngest leader at 55, is seeking a second five-year term. If he loses, he'll make history as the only incumbent president not to win re-election.Kenyan President Uhuru Kenyatta casts his vote on Tuesday.

Odinga, who's running for president for the fourth time, served as prime minister between 2008 and 2013 and is the incumbent's main challenger.

Independent Electoral and Boundaries Commission (IEBC) spokesman Andrew Limo said turnout looked "huge" as Kenyans cast ballots at more than 40,000 polling stations on Tuesday.

Limo acknowledged claims of malfunctioning voting machines, which have circulated online, saying there have been "three or four cases of malfunction where the system needed restarting" but added that for the most part things have "gone well."Kenyans wait in line at a polling station in Eldoret on Tuesday.Voters line up at a station in Kibera.Inmates vote at Kisumu prison. This is the first time that inmates in Kenya are allowed to vote; they are only permitted to vote for presidential candidates.

The IEBC said in a statement that extra ICT support staff have been brought into service to resolve minor technical issues.

Videos circulated on social media of skirmishes and tear gas allegedly being used in some parts of the country, but CNN has not witnessed any evidence of violence thus far. The atmosphere at several polling stations in Nairobi was relaxed as Kenyans came out in droves, eagerly queuing in orderly lines to vote.

"We are eager to choose our leaders, even in the rain," one voter, Susan Mukami, told CNN at the Moi Avenue Primary School polling station located in Nairobi.

Kenyan YouTube personality and radio presenter Xtian Dela said he'd waited four hours to cast his first ever vote in Nairobi.

"[I] am super excited about the election this year ... I just had to exercise my civic duty: To hire and fire my employees," he told CNN.