Updated

Kenyans are voting in an election that pits President Uhuru Kenyatta against challenger Raila Odinga in an East African economic hub known as much for its relative, long-term stability as the ethnic allegiances that shadow its democracy.

A key concern after polls opened Tuesday was whether Kenya would echo its 2013 election, a mostly peaceful affair despite opposition allegations of vote-tampering, or the 2007 election, which led to violence fueled by ethnic divisions that killed more than 1,000 people.

Reaction to the result could partly depend on the performance of Kenya's electoral commission, which will collect vote counts from more than 40,000 polling stations. Kenya has nearly 20 million registered voters.

Former U.S. Secretary of State John Kerry is among thousands of observers who are monitoring the election.