Somalis uprooted by fighting in Mogadishu looted trucks carrying UN food aid on Friday, peacekeepers said, highlighting what relief agencies warn is a fast deteriorating humanitarian catastrophe.

Somalia now has 1 million internal refugees, aid workers say, and their numbers increase by an exodus of some 20,000 civilians each month from the capital, where Islamist insurgents are battling the Ethiopian-backed government.

Captain Clement Cimana, spokesman for a small African Union peacekeeping force in the coastal city, said the displaced residents targeted trucks carrying supplies for the UN World Food Programme (WFP) before local police restored order.

'They also blocked the main road, showing their anger,' he said. 'They said they always see WFP-chartered trucks full of food passing in front of them while they are hungry.'

A WFP spokesman in Somalia said relatively small amounts of sorghum and vegetable oil had been stolen, but that almost all the food had subsequently been recovered.

Aid agencies say record high food prices, hyper-inflation and drought across the country are exacerbating the crisis and will worsen if seasonal rains due next month fail as expected.

Meanwhile, police and witnesses in Merka, south of Mogadishu, said a small unmanned plane had crashed near the coast. Local media speculated it was a US surveillance drone controlled from a warship in the Indian Ocean.

The US military has launched several air strikes in Somalia in recent months, targeting Al Qaeda suspects including the bombers of the US embassies in Kenya and Tanzania in 1998.-Reuters