Of Kenya's population of 48 million, 19 million were registered to vote in elections that are also choosing members of parliament and local representatives in the country's devolved counties. It is not yet clear when that will happen.
Raila Odinga reacted to the provisional results earlier this Thursday.
Worldwide election observers have said they saw no signs of interference with the vote.
The slain election official was working for the ruling Jubilee party, Hassan Barisa, a resident of Hola in Galole, said.
At least two of attackers were killed by police, said Larry Kieng, regional police coordinator.
Nairobi- Kenya slipped a little deeper into violence on Wednesday after the former prime minister Raila Odinga rebuffed the final results of the recent presidential elections. "We recognize the tallying of results at all levels is a critical part of the process", the groups said.
Turnout showed that renewed outgoing president Uhuru Kenyatta won for another term.
"We are supposed by now to have had results, but the delay has been caused by the fact that the opposition had complaints about the system of transmitting results", Mogambi said.
"You can only cheat the people for so long", Mr. Odinga added.
NAN reports that in 2007, tallying was stopped and the incumbent president declared the victor, triggering an outcry from Odinga's camp.
Fred Matiang'i (Front), current acting Kenyan Cabinet Secretary for the Ministry of Internal Security and Coordination, addresses the press in Nairobi, capital of Kenya, Aug. 9, 2017.
Global stocks slide as US-N. Korea nuclear tensions rise
After a dip of as much as 0.52 percent earlier in the day, Wall Street's three major indexes bounced off intraday lows. London's benchmark FTSE 100 index fell back 1.1 percent to 7,415.78 points, driven by losses in the commodity sector.
At midday, clashes between police and rioters had eased, but tensions can still be felt in Mathare district and the western city of Kisumu, where the first clashes broke out early.
The commission's Chairman Wafula Chebuati said that so far they had not seen a discrepancy in the preliminary figures being published from the figures in the 34As.
The commission said that verifying and confirming of election returns were ongoing and that they have received over 40,000 form 34As.
Kenyatta has not commented on Odinga's allegations.
Kerry is leading a mission of election observers who have monitored the vote and its aftermath. Other observer missions include the Carter Foundation and the European Union.
Mahama noted that the "opening, voting, closing and counting process at polling stations were credible, transparent and inclusive". Election officials are investigating. "The streets do not".
Mbeki said the matter was looked into by the AU election observer mission, which was one of many.
As of 0300 GMT, the election commission website put Kenyatta ahead by 55.1 per cent of votes counted to 44 per cent for Odinga, a margin of almost 1.4 million ballots with more than 80 per cent of polling stations reported.
"Our election management system is secure".