The world's biggest refugee camp has run out of space, creating a "humanitarian emergency" in part of northeastern Kenya, an international medical organization says.

Doctors Without Borders says the Dagahaley, Hagadera and Ifo camps — known collectively as the Dadaab refugee camps — are experiencing severe overcrowding and a shortage of supplies.

The report, titled "No way in: The biggest refugee camp in the world is full" says arriving refugees wait an average of 12 days to receive their first ration of food, and 34 days to receive cooking utensils and blankets from the UN refugee agency.

"Until then they must fend for themselves in a hostile semi-desert environment," the report says.

The camps were built 20 years ago, and were initially established to house up to 90,000 people fleeing conflict in neighbouring Somalia.

The border between Somalia and Kenya was closed in 2007, but people continued to move across the border.

The UN refugee agency said in 2008 that there were no more plots of land available to new arrivals. But refugees kept coming, settling in space on the margins of the camps and outside the perimeter.

The UN refugee agency estimates that roughly 350,000 people are now living in the camps. By 2011, as many as 450,000 people will be living there, the agency estimated.

"Unless urgent action is taken to ease the overcrowding and improve the provision of services, living conditions for the refugees — both the recent arrivals, and those who have been there for years — will become intolerable, and public health outbreaks will become increasingly likely," the report says.

The medical organization urged Kenya and the UN refugee agency to open a partially completed camp known as 'Ifo Extension' and called on officials to take measures to ease the overcrowding.