At least 36 people have died in a head-on collision between a lorry and a Nairobi-bound bus on a notoriously dangerous road near Migaa in Kenya.
Local officials said the accident happened at 03:00 (0:00 GMT), and the bus was speeding and in the wrong lane.
The World Health Organisation (WHO) has ranked Kenya as one of the world's worst countries for road safety.
Police believe over 100 people have died in the same area on the Nakuru-Eldoret highway in recent weeks.
The bus was reportedly carrying 46 passengers to Nairobi from the western town of Busia when the accident happened.
"I was asleep when the accident occurred and all I heard was a loud bang and screams from all over before I was helped out," a passenger who survived the crash told a local radio station.
Both vehicles' drivers are said to be among the dead, with the youngest victim reportedly a three-year-old child.
The Kenyan Red Cross said on Twitter that 18 passengers from the bus were taken to hospital with serious injuries.
Six of the injured later died, officials say.
Police say the accident on Sunday is the worst on the highway in the month of December.
The National Transport and Safety Authority announced an immediate ban on overnight travel for long-distance buses following Sunday's crash.
Earlier this month Kenyan officials announced the road was going to be renovated into a dual carriageway in 2018, in order to try and minimise accidents on the deadly stretch.
Security has been stepped up in the Kenyan capital, Nairobi, ahead of the inauguration of President Uhuru Kenyatta for a second term in office.
More than 20 heads of state or senior ministers are expected to attend.
Opposition leader, Raila Odinga, who boycotted a re-run of the presidential poll, has called for a protest rally, despite a police ban.
August's presidential election was annulled by the Supreme Court over what it called "irregularities".
The re-run, on 26 October, saw Mr Kenyatta win 98% of the vote with a turnout of just under 39%.
Tuesday's ceremony at a sports stadium in Nairobi is due to get under way at 10:00 local time (07:00 GMT).
Organisers are expecting about 60,000 people to fill the venue and giant screens have been set up outside for those unable to get in.
President Kenyatta's deputy, William Ruto, will also be sworn in.
Among the foreign leaders expected to attend will be Israeli Prime Minister Benjamin Netanyahu, Ugandan President Yoweri Museveni and Rwandan President Paul Kagame.
The Kenyan opposition coalition has called on its supporters to boycott the inauguration and instead hold a rally in memory of people killed in clashes since August's election.
The police have warned the coalition against holding the event.
Kenya's Supreme Court took the unprecedented decision to annul the 8 August presidential election and demand a new poll in September citing "irregularities and illegalities".
Chief Justice David Maraga said the election had not been "conducted in accordance with the constitution" and declared it "invalid, null and void".
The court said the result was "neither transparent nor verifiable".
Mr Odinga then urged his supporters to boycott the second vote because he said no reforms had been made to the electoral commission since the original poll.
However the re-run went ahead in October and the Supreme Court has since validated the results, but correspondents say the election dispute has left Kenya deeply divided.
Kenya's Supreme Court has upheld President Uhuru Kenyatta's victory in last month's election re-run, which was boycotted by the main opposition.
Judges dismissed two petitions challenging the poll, opening the way for Mr Kenyatta to be inaugurated for a second term next week.
The opposition said the ruling had been given under "duress", and it would not recognise the new government.
Mr Kenyatta won with 98% of the vote with turnout at 39%.
The poll was held after the Supreme Court annulled elections held in August, saying the poll was marred by "irregularities and illegalities".
Civil society groups wanted the new poll to be annulled as well, arguing that the electoral commission had violated the law by failing to call for fresh nominations.
Handing down the verdict on behalf of six judges, Chief Justice David Maraga said: "The court has unanimously determined that the petitions are not merited"
The aftermath of the poll has been fraught with tension.
Last week, five people were killed as police tried to break up a convoy of the opposition National Super Alliance (Nasa) in the capital, Nairobi.
Nasa candidate Raila Odinga refused to take part in the re-run, saying the electoral commission had failed to take steps to ensure that mistakes of the August election would not be repeated.
"We in Nasa had repeatedly declared before this Supreme Court ruling today that we consider this government to be illegitimate and do not recognise it. This position has not been changed by the court ruling," Mr Odinga's adviser, Salim Lone, said in a statement.
Five people have been killed in Kenya's capital Nairobi as police broke up crowds of opposition supporters.
At least two of the victims were shot dead, reports said, while others may have been stoned to death by a mob.
Riot police were present but did not use any live rounds, a police spokesman said, blaming the deaths on the crowd.
The supporters of the opposition National Super Alliance (Nasa) had gathered to welcome home its leader, Raila Odinga, from an overseas trip.
On Monday, the Supreme Court is due to rule on the legality of last month's re-run election, won by the incumbent Uhuru Kenyatta with 98% of the vote.
The vote was widely boycotted by the opposition and denounced by Mr Odinga as a sham. He went away on a 10-day speaking tour in Europe and America after withdrawing from the election.
On Friday, Mr Odinga's convoy snaked through Nairobi to avoid security forces who tried to block off routes to public grounds where a rally could convene, the BBC's Tom Oladipo reports from the city.
Demonstrators threw stones in response. A police truck was set on fire. Police spokesman George Kinoti said in a statement that officers had used only teargas and a water cannon.
"No live fire was used," he said. "We are however aware that sections of the mobs accompanying the Nasa convoy, looted property and five persons were killed by stoning in different incidences after having been caught stealing by enraged crowds."
Mr Odinga has called for a "national resistance movement" to "restore democracy" following last month's vote, in which turnout was only 39%.
"Today is the day we are launching Kenya as a third republic," he said from his car on Friday, to cheering supporters.
"What you have seen is a signal that a third liberation is coming soon," he added.
Kenyan opposition leader Raila Odinga has rejected the results of the re-run presidential election that saw Uhuru Kenyatta gaining a second term.
Mr Odinga called it "a sham" but made no mention of any legal challenge.
Mr Kenyatta won 98% of the vote with turnout under 40% - less than half that recorded in August's vote, largely because of an opposition boycott.
The Supreme Court annulled the first vote in August citing "irregularities and illegalities".
In his first official reaction to the re-run, Mr Odinga called for a "national resistance movement" including the formation of a "people's assembly" to bring civil society groups together to "restore democracy". But he did not explain how that would work.
"This election must not stand .... It will make a complete mockery of elections and might well be the end of the ballot as a means of instituting government in Kenya. It will completely destroy public confidence in the vote," he said.
The BBC's Alastair Leithead in Nairobi says that Mr Odinga's response to the election result was short on substance.
The opposition leader repeated claims that the re-run of August's presidential poll was unconstitutional - lawyers from both sides are still arguing about this, and the Supreme Court has a petition pending.
"We will not allow two megalomaniacs [Mr Kenyatta and his deputy] destroy the dream of freedom and democracy," Mr Odinga said.
Mr Kenyatta, who is now set to serve a second term, said if the new results were challenged in the courts he would accept the outcome.
He has appealed for calm and promised Kenyans that "their neighbour will remain their neighbour" despite political uncertainty.
About 50 people are reported to have died in violence since Mr Kenyatta was declared the winner of August's election.