In recent days, opposition officials have described the election results as a fraud and claimed that Raila Odinga, the 72-year-old Nasa leader, was the legitimate victor.
As Kenyatta held a strong lead in provisional results with 96 percent of all polling stations counted, the election commission defended the voting system as secure, saying there were "no interferences before, during and after" Tuesday's election.
The IEBC, which spent about U.S. $500 million on the new biometric voting system, has dismissed Odinga's claims but admitted there had been unsuccessful attempts to hack the system.
A group of labourers and transporters sitting in the shade said they were eager for daily life to return.
Police fired tear gas at rock-throwing opposition supporters in one Nairobi neighbourhood, residents said, but most of the capital and the rest of the country were calm after four people were killed in election-related violence on Wednesday.
Global observers have praised the handling of the election, with the European Union saying it had seen no sign of manipulation despite opposition complaints and scattered protests.
Turnout was 78.91 per cent, down from almost 85 per cent in 2013, electoral commission chief Wafula Chebukati said, describing the process as "credible, fair and peaceful". Nasa has complained of fraud and hacking, but the election commission has defended its process and says the results published are accurate.
"Why are they shooting at innocent people who are expressing their views?" said a protester in Kisumu, a city in Kenya's west where there is little love for Kenyatta.
Peaceful elections in East Africa's largest economy would help provide stability to the region but allegations of vote rigging have sparked concern with some Kenyans fearing ethnic clashes similar to those triggered a decade ago. "The chairman told us ... they will respond to us after the event", said Mudavadi.
Earlier on Friday, the opposition, led by Odinga, who has lost the last two elections amid complaints of fraud, said it rejected the process after its complaints had not been addressed.
Mr. Mahama said inspite of the allegations, the integrity of the elections was intact. An opposition alliance's backing for Mr Odinga was not enough to stop Mr Kenyatta's re-election.
The announcement of the results was delayed for hours, after election officials said they needed time to review some documents from some polling districts.
However, in 2013, the failure of key features of this new technology led Odinga and his supporters to claim that, once again, an election had been stolen.
Between Dec. 28, 2007, and February 28, 2008, at least 1,000 people died and 600,000 were displaced from their homes, after President Mwai Kibaki was declared the victor and Odinga rejected the polls as rigged. Kenyatta's government has also spurred growth by encouraging the development of the tourism, agriculture, services and manufacturing industries, and made some headway in improving access to education and health care.
Former US secretary of State John Kerry, who served as an election observer for the Carter Center, said Thursday that while there were "little aberrations here and there", the election was not rigged. What is happening is that people just want to see justice. "Let us always remember that we are brothers and sisters".
He said that if losers "graciously" accepted election defeat, they would end up being winners.