More than 100,000 people displaced by inter-religious violence in Central African Republic are sheltering at a makeshift camp at Bangui airport, a medical charity has said, calling for urgent aid.

Medecins Sans Frontiers (MSF) said it was receiving between 15 and 20 wounded a day at the site from fighting in the riverside capital, where the deployment of French and African peacekeepers in early December has failed to halt violence.

Attacks by Muslim Seleka rebels, who seized power in March, and Christian militias have killed more than 1,000 people and displaced an estimated 400,000 in Bangui this month.

MSF said the airport camp, which stretches for kilometres beside the runway, lacked proper sanitation as well as supplies of food and water as UN agencies have failed to keep pace with the scale of the problem.

"If nothing is done in the next two weeks there is a risk of an epidemic breaking out," said Lindis Hurum, MSF coordinator at the airport camp.

"MSF demands an increase in the emergency actions being taken by humanitarian agencies."

Without proper infrastructure at the camp, thousands of families are sheltering from the tropical sun under cardboard boxes or makeshift tents made of blankets tied to sticks.

Despite the conditions, a spike in violence in recent weeks has driven tens of thousands of people to airport, which is patrolled by Burundian soldiers from the African Union peacekeeping force (MISCA) and lies next to a French military base.

'Catastrophe'

French troops in armoured vehicles guard the main gates.

"We are short of everything here. Food is scarce," said Samuel Degoto, 49, a teacher, who fled from his home in northern Bangui with his wife and seven children, carrying only a few bags.

"If nothing is done before the next crisis strikes, there will be a catastrophe."

The United Nations launched an appeal on Friday for $152 million to help meet emergency humanitarian needs such as drinking water and sanitation in makeshift camps in the former French colony.

It estimates that more than 800,000 people are displaced across the country as a whole.