Aid groups on Sunday warned of a looming humanitarian emergency after post-election violence in Kenya as teams struggled to access tens of thousands of displaced civilians across the country.
With widespread insecurity and supplies close to depletion, field teams said their worst fears were mainly for the country's western region.
"Food and clean water supplies are now running dangerously low, especially in and around (the western city of) Kisumu," said Wubeshet Woldermariam, country director of the Merlin medical charity.
"People are being forced to drink unsafe water, risking diarrhoeal diseases, infection and dehydration. The longer the crisis continues, the greater the risk to people's health," he warned in a statement.
"If peace isn't restored within the next few days, disease outbreaks and severe dehydration are very real threats."
At least 361 people died in poll-related violence since the December 27 election, according to a tally compiled by AFP with hospital, police and mortuary sources.
The UN estimates that the chaos may have displaced 250,000 Kenyans, some 100,000 of whom need immediate help in western Rift Valley region. The United Nations refugee agency UNHCR has pledged to provide aid.
Local aid workers feared an outbreak of diseases in crowded makeshift camps in schools, hospitals and churches, most of which were still out of reach owing to their inaccessibility or safety concerns.
The Kenya Red Cross Society said it faced challenges in distributing supplies to those displaced in Nairobi, where slum dwellers lost possessions to looters and in fires.
"The challenge we are facing is that we need 100 percent blanket distribution, and security is also still a problem," Abdi Shakur told AFP.
Hundreds of families were crammed inside a cathedral in the western city of Eldoret, still fearing for their lives after at least 35 people died there last week in an arson attack on a church.
Thousands of others huddled in makeshift cardboard shacks in the volatile town of Molo, in the Rift Valley province, aid workers said.
"All this is a recipe for disaster," said a Red Cross worker.
Meanwhile, the UN's World Food Programme (WFP) said insecurity and roadblocks set up by vigilante groups had barred food trucks from the port city of Mombasa from reaching their destination.
"At the moment we have not had a problem in food distribution but if this situation continues then food will not get delivered on time," a WFP spokesman said in a statement.
The government has instructed the military to escort trucks delivering supplies across the country to avoid highway ambushes.
The UN Children's Fund (UNICEF) said many hospitals in the disaster zones were in need of medical supplies to treat a wide range of injuries and conditions.
"Supplies and staff are needed to treat victims of shooting, burning, beating, slashing and trampling," said Sara Cameron, the agency's communication officer in Kenya.
The UN Office for the Coordination of Humanitarian Affairs (OCHA) estimates that around 5,000 Kenyans have fled to Uganda, where they live in schools, churches and with relatives, while an unconfirmed number have also left for Tanzania.
On Friday, the International Committee of the Red Cross appealed for 15 million Swiss francs (13 million dollars, nine million euros) to deal with the unprecedented crisis in the east African nation.
Violence erupted in Kenya a week ago after the country's electoral panel declared President Mwai Kibaki the winner of the disputed December 27 polls. His main rival, opposition chief Raila Odinga, said the result was fixed.