The electoral commission admitted that hackers had tried to access its database, but said they did not succeed.
Early results put the incumbent Uhuru Kenyatta of the Jubilee Party ahead of his arch rival Raila Odinga of the National Super Alliance.
On Wednesday, at least three people were shot and killed in confrontations between security forces and opposition supporters in several areas of Kenya, East Africa's commercial hub whose stability is a key concern for the region.
On Wednesday morning, the election commission website showed Kenyatta leading with 54.4 percent of the votes against 44.8 percent for Odinga, a margin of almost 1.4 million votes, after 94 percent of the votes were counted.
The leading candidates have avoided using inflammatory rhetoric that could fuel tensions ahead of the vote, global election observers said. That year, following a poll that was reportedly full of irregularities, Odinga's loss sparked deadly ethnopolitical violence, leaving some 1,100 people dead and 600,000 displaced.
The Intergovernmental Authority on Development (IGAD), the African Union, the European Union and the African Electoral Observation Group had earlier said the election was credible.
As the final results deadline approaches, we shall see what transpires with this election!
"We have caught them".
The claims, which have not been verified, tie into the narrative supported by the opposition party during the campaign that the ruling party meant to steal the election.
Election commission Chairman Wafula Chebukati acknowledged that an attempt to hack the voting system was undertaken on polling day, but that it failed.
Kenya's electoral commission called on Kenyans to remain "calm" on Wednesday night (Aug. 9), after protests erupted in parts of the country over inconsistencies of provisional results.
Former Ghanaian president John Mahama, who is leading the Commonwealth delegation, also urged Kenyans to give the IEBC "proper time and space to complete the results process with necessary due diligence".
Demonstrator Sebastian Omolo, a supporter of Mr Odinga, said: 'He is not accepting the results and that is why we are on the streets but police have started shooting'.
"When we made our statement yesterday we knew [IEBC is the one to declare results]".