The UN's World Food Programme was preparing on Tuesday to airlift food aid into the Somali capital Mogadishu, but efforts were hampered by last minute paperwork in Kenya.

"We are still hoping it will take off today," said WFP spokesman David Orr, noting that the flights had a narrow timeframe to take off, offload food and then return to Nairobi.

"If not it will be going ahead on Wednesday," he said, adding that the flights were waiting only for clearance forms to be completed before taking off.

An estimated 3.7 million people in Somalia -- around a third of the population -- are on the brink of starvation and millions more in Djibouti, Ethiopia, Kenya and Uganda have been struck by the worst drought in the region in 60 years.

The UN last week officially declared a famine in two regions of southern Somalia.

The WFP flights will be carrying around 14 metric tons of high energy food aimed to combat malnutrition, especially in children.

Flights will also go to the Ethiopian town of Dolo on the border with Somalia and to the town of Wajir in northern Kenya.

Other organizations have already made relief deliveries, with the UN children's agency airlifting five tonnes of aid into rebel-held part of southern Somalia earlier this month.

The International Red Cross on Sunday said it had handed out 400 tonnes of food in drought-hit areas controlled by the hardline Shebab insurgents, the first ICRC-led drops into such areas since 2009.

The WFP was forced to pull out of southern Somalia last year after a series of threats and curbs on its operations from Shebab rebels, but it has continued to operate in Mogadishu and central and northern regions of the war-torn country.

In Mogadishu alone, WFP assists approximately 300,000 people and it has been scaling up operations with three new centres to feed the large numbers of internally displaced people flooding into the city from the south.