NAIROBI, Kenya (CNN) -- The result of Kenya's election looked set for a dramatic climax as the country's electoral commission said Saturday that incumbent president Mwai Kibaki was closing the gap on opposition leader Raila Odinga.
Supporters of presidential candidate Raila Odinga celebrate in Nairobi.
Odinga's party had earlier claimed victory in the election, which has been blighted by violent clashes between rival supporters.
The party's number two official, Musalia Mudavadi, told a press briefing that Odinga had received 4,215,437 votes to Kibaki's 3,748,261 -- figures he said came from party representatives at polling stations across the country.
However, electoral commission officials told reporters later in the day that the gap between the two men had narrowed to between 50,000 and 60,000 votes with around 20 out of 210 constituencies still to declare.
In a press briefing that quickly became a shouting match between officials from the two main parties, commission chairman Samuel Kivuitu said they were investigating claims of fraud after results from one station exceeded the number of votes cast by 50 percent.
Mudavadi, from the Orange Democratic Movement, had earlier called on Kibaki to "acknowledge the will of the Kenyan people and concede defeat" to help end a tide of violence he said had been provoked by the extended delay in releasing the results.
If Kibaki were to lose it will be the first time an incumbent leader has been unseated at the ballot box in the country's history.
An electoral commission spokesman told CNN the victory claims were "insignificant" because "it's official results which count."
Kenya's electoral commission has not yet announced official results of the election. It is expected to do so later Saturday.
But the slow pace of the vote counting has sparked violence in some parts of the country.
The delay comes from rules requiring that ballots be hand-counted on site and then sent to Nairobi for verification before results can be announced.
The lag in the revelation of the results is blamed for the outbreak of sporadic violence in some areas.
Roaming gangs armed with machetes and other homemade weapons burned shops and broke into the homes of their political opponents Saturday in Kibera, the largest slum in Kenya's capital.
CNN Producer Kim Norgaard and his crew witnessed gangs looting and then burning several stores, and visited the home of a local organizer of one of the ruling parties that had been set on fire early Saturday morning.
The man was taken to the hospital with machete wounds, Norgaard said.
People's homes are being targeted according to their political affiliations, and armed gangs blame rival ethnic groups affiliated with local political parties for the violence.
Police are out on the streets but seem outnumbered and unable to completely stop the burning and looting, Norgaard observed.
He said gangs trying to make their way into central Nairobi were being repelled with tear gas by police on the edge of the Kibera slum.
Kibaki's leadership is facing a serious challenge from Odinga, a flamboyant politician who has accused his rival of corruption. They are allegations Kibaki has faced since soon after he came to power five years ago.
While many Kenyans say they are tired of the accusations and are hungry for change, many others credit Kibaki with keeping the country's economy strong.
Many others, however, don't feel they have benefited from the economic boom and accuse Kibaki of favoring members of his own Kikuya tribe, which has dominated Kenyan politics since independence.
Odinga, who hails from the minority Luo tribe, has won support from the rural and urban after promising to share the wealth among all the people.
A peaceful election and a smooth transition of power are seen as crucial for Kenya, a stable country in an otherwise-volatile region.
Voters were also choosing members of parliament and civic leaders. E-mail to a friend