The head of the United Nation's refugee agency describes the drought in Somalia as the "worst humanitarian disaster" in the world and urges Kenya to build more camps, after touring the region.

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Antonio Guterres, the head of the United Nations High Commission for Refugees (UNHCR) has urged Kenya's president Mwai Kibaki to open a new camp for people fleeing drought and war in Somalia.

Guterres met refugees at the Dadaab camp, the world's largest refugee camp in the world, and appealed for "massive support" from the international community to help over 380 000 people in Dadaab.

It was built to house 90,000 people but could soon be holding 500,000, aid workers say.

"I have no doubt that in today's world, Somalia corresponds to the worst humanitarian disaster. I have never seen in a refugee camp people coming in such desperate conditions," Guterres said.

Read more: Channel 4 News talks to the head of the UN in Somalia

"Here in the outskirts of the Somali refugee camp of Dadaab, we have the poorest of the poor and the most vulnerable of the vulnerable in the world," he continued.

A woman waits with her child for medical treatment at Aden Adde hospital near a displaced persons camp in Waberi (Reuters)

Guterres went onto urge aid agencies to enter Somalia, after the militant group al-Shabaab - who control central and southern parts of the country - said it will allow foreign workers to operate.

we have the poorest of the poor and the most vulnerable of the vulnerable in the world, Antonio Guterres, head of UNHCR

Some 12 million people are said to be affected by the Horn of Africa's worst drought in 60 years.

Around 3000 people are fleeing each day from Somalia, which has been afflicted by 20 years of civil war.

New Camp

Gutteres was due to meet the Kenyan Prime Minister after his tour, but the appointment was called off at short notice.

The UNHCR have called on the Kenyan government to authorise the completion of a new facility, the Ifo II camp, which has room for up to 40 000 people.

But the Kenyan government has so far refused to do so, with some officials claiming a new camp may encourage refugees to stay in the country permanently.

In pictures: Drought in the world's largest refugee camp