Violence in the Central African Republic has uprooted nearly a million people - a fifth of the population - and hampered aid efforts in the capital Bangui, according to the UN refugee agency (UNHCR).
A flare-up in violence between Muslim fighters and Christian militias has displaced more than 200,000 people in the past few weeks alone, leaving a total of 935,000 homeless, UNHCR said on Friday.
The number of people sheltering at a makeshift camp at the international airport has doubled in the past week to 100,000, but while the site lacks proper access to food and water, fierce fighting in nearby neighbourhoods has restricted aid access.
"Insecurity and chaos around the site... prevents us from doing any distribution," UNHCR spokesman Babar Baloch told a news conference in Geneva.
"It's a horrible situation. We have heard a lot about revenge attacks happening inside health centres, where armed elements have gone and attacked patients."
A Muslim rebel group, the Seleka, unleashed a wave of killing and looting after seizing power in March. The deployment of 1,600 French and nearly 4,000 African Union peacekeepers has done little to contain the tit-for-tat violence between religious communities.
In the riverside capital alone, more than 510,000 people have been displaced - equivalent to more than half the city's population, UNHCR said.
Medical charity Doctors Without Borders said it was cutting services to a minimum at its airport clinic after stray bullets killed three children and injured 40 people this week.
"We are not going to continue to put the lives of our personnel at risk," Lindis Hurum, its coordinator at the site, told the Reuters news agency. "A team composed of five of our 16 doctors will be left in place for cases of extreme emergency."
Many of the displaced and injured inside the airport camp said they feared they were being abandoned.
"I owe my life today, like hundreds of others here, to MSF [Doctors Without Borders]. But with this suspension of their activities, it will be a massacre," said resident Saint Cyr Lamaka.