Long-time Kenyan opposition leader and the man who Kenya's elections board says finished second in the country's August 9 presidential election finally spoke on the matter on Tuesday afternoon.

Odinga has rejected Kenya's Independent Election and Boundaries Commission (IEBC) Chairman Wafula Chebukati's declaration of William Ruto as president-elect and said his coalition is pursuing all available constitutional options.

On Monday, Chebukati declared Ruto as the winner with 7,176,141 votes or 50.49 percent of the total votes cast. Odinga received 6,942,930 votes or 48.85 percent of the vote.

Odinga announced his rejection minutes after four members of the seven-member IEBC addressed the media to explain their decision to disown the result of the presidential poll, saying the final tallying process had been "opaque".

Odinga claimed Chebukati showed disregard to Kenya's constitution by announcing results processed unilaterally despite the objections of the four commissioners.

"We understand that only Mr Chebukati alone had access to the tally of the presidential vote and they only came to know the tally a few hours to the time of announcing. The figures announced by Mr Chebukati are null and void and must be quashed by a court of law."

Monday's events raised concerns about violence seen in past Kenyan presidential races, particularly the 2007 campaign which saw more than 1,200 people killed in post-election violence. Odinga urged citizens to remain calm.

"Let no one take the law into their own hands.  We are pursuing constitutional and lawful channels and processes to invalidate Mr. Chebukati's illegal and unconstitutional pronouncement.  We are certain that justice will prevail," said Odinga.