Kenya's electoral commission chairman has admitted its database was a target of an unsuccessful hacking attempt, but it has failed to convince the opposition, which continues to dispute the results.

Wafula Chebukati's remarks came on Thursday following allegations by opposition leader Raila Odinga that hackers infiltrated the database and manipulated results in favour of President Uhuru Kenyatta after Tuesday's vote.

Chebukati said "hacking was attempted but did not succeed" and tallying of final results was continuing.

With results from 99 percent of polling stations counted, Kenyatta held a strong lead.

Britain and the US joined foreign observer missions from the European Union, African Union, Commonwealth and the Carter Center in urging party leaders to be patient and refrain from inflaming tensions ahead of the release of final results, expected on Friday.

But the opposition National Super Alliance (NASA) doubled down on accusations the counting process was a "sham" after Odinga claimed on Wednesday that hackers broke into the electronic tallying system and manipulated results.

READ MORE: Why are Kenya's elections so bitterly contested?

One of NASA's leaders Musalia Mudavadi provided documents purportedly obtained from the servers of the electoral commission (IEBC) via a "confidential source" showing that Odinga had 8.04 million votes, leading Kenyatta on 7.75 million.



This was despite the fact that results streaming onto the IEBC website showed Kenyatta with 8.1 million votes to Odinga's 6.7 million.

"We demand that the IEBC chairperson announce the presidential election results forthwith and declare Raila Amolo Odinga... as the duly elected president," said Mudavadi.

Hundreds of Odinga supporters, mainly young men, poured onto the streets of the opposition stronghold of Kisumu in celebration. At least one truck of anti-riot police followed them, a Reuters witness said. There were pockets of similar celebrations in opposition strongholds in Nairobi as well.



IEBC chief Wafula Chebukati rejected this demand, saying the commission would only announce final results once all the forms from constituencies had arrived at the tallying centre in Nairobi and been validated.

Earlier, a team headed by former US Secretary of State John Kerry also called for calm and restraint on Thursday, as protests called by the opposition turned violent on Wednesday, claiming the lives of at least five people.

Kerry also told Al Jazeera that the allegations need to be examined but were "not a reason to stop the process or question the entire election".

READ MORE: In Kenya's Kisumu, prayers for 'Baba' Odinga's presidency

Al Jazeera's Catherine Soi, reporting from the opposition stronghold Kisumu, said she spoke with Odinga's campaign team members and close advisers, who still insist that the voting system was hacked.

"Raila Odinga says he needs an independent investigation into the poll and people here are saying that they have every confidence in him. They will believe everything he is going to say," she said.

Odinga's claims were enough to spark isolated protests in his strongholds in several Nairobi slums and the western city of Kisumu on Wednesday.

A relative peace returned to the streets on Thursday. There were violent protests in one Nairobi neighbourhood, Kawangware slum, where police fired live rounds and tear gas as they clashed with opposition supporters.

And later on Thursday, Mohamud Saleh, north eastern regional coordinator, said police was trying to restore calm in the county of Garissa where a town market was burnt by arsonists amid an opposition protest.