Kenyan police have used tear gas to disperse angry supporters of political parties during clashes over the outcome of primaries across the country.
President Kibaki is seeking a second term
Several people, including a minister and former MPs, were injured as the results of the primaries were disputed.
Candidates had to register by Monday but the exercise was marred by chaos and violence.
Incumbent Mwai Kibaki faces a strong challenge from former minister Raila Odinga in the presidential race.
The Orange Democratic Movement (ODM), Party of National Unity (PNU) and ODM-Kenya are the three main parties fielding candidates at the elections.
Latest opinion polls show ODM leader Raila Odinga remains the most popular candidate with 45% of Kenyans backing his bid, compared to 41%, who support President Kibaki, running on a PNU ticket.
But analysts say the outcome of the primaries, which saw party officials in both the ODM and the PNU clearing defeated candidates to contest the polls, may affect the chances of the two leaders in the December poll.
Assistant minister John Serut was admitted to hospital with serious injuries after his opponents attacked him at the headquarters of the former ruling party Kanu.
He was accused of trying to be registered as a candidate after an allegedly flawed nomination exercise.
Dozens of policemen have been deployed at various party headquarters in the capital to control rowdy crowds protesting against favouritism during the nominations exercise.
Wangari Maathai was defeated in a PNU primary
Several former MPs defeated at the primaries held by the main parties have defected to small political parties, which were formed just months before the general elections.
Nobel prize-winner Wangari Maathai was among the prominent politicians who lost at the weekend primaries.
Prof Maathai was defeated by a newcomer in the race to become a PNU parliamentary candidate.
She has now been cleared by the little known Mazingira party to contest a seat in central Kenya.
Meanwhile, police spokesman Eric Kiraithe has said they have launched a manhunt for individuals who purchased dozens of machetes from a leading supermarket chain within a period of two days.
Mr Kiraithe said managers of the Nakumatt supermarket chain had raised the alarm after noticing the purchases.
Electoral Commissioner Jack Tumwa announced that certificates issued to candidates after the 19 November deadline would not be accepted.
Mr Tumwa said so far 80 political parties have been cleared to participate in the general elections.