Kenyans are voting in a contentious presidential election rerun, boycotted by the country’s opposition leader.

Polls opened at 6am local time (3:00 GMT) and will close at 5pm (14:00 GMT). More than 19-millions voters are registered to cast their vote in the election.

The country is holding an election rerun after the August 8 presidential poll results were nullified by the country's Supreme Court because of "irregularities and illegalities" in the voting process.

President Uhuru Kenyatta, 55, is seeking a second and final five year term in office. He won 54 percent of the votes in the nullified poll.

His main challenger, Raila Odinga, who received almost 45 percent of the votes in August's election, is boycotting the vote.

Odinga, 72, said opposition demands to reform the electoral body following the court ruling have not been met.

Odinga, who successfully challenged the results of the August poll, has called on his supporters to stay away.

"Do not participate in any way in the sham election. Convince your friends, neighbours and everyone else to not participate," Odinga told his supporters at a rally in Nairobi on Wednesday.

"We advice Kenyans who value democracy and justice to hold vigilance prayers or stay at home."

Quorum of judges

Kenyatta is the country's founding father while Odinga, a former prime minister, is the son of the country's first vice president.

On Wednesday, the Supreme Court was unable to raise a quorum of judges to decide on whether the poll should go ahead.

The petition was brought by three human rights activists who claimed the electoral commission is not ready to hold a credible poll.

The East African country has witnessed almost daily street protests following the announcement of August's presidential election result.

At least 49 people have been killed in the political violence since the poll.