The U.N. World Food Program says an airlift of food to the drought-stricken Horn of Africa has been postponed until at least Wednesday.

The airlift was due to begin Tuesday, but a WFP communications officer tells VOA that the flights have been held up by logistical problems in Kenya.

The WFP said Monday that planes will carry food to Somalia's capital, Mogadishu, eastern Ethiopia, and northern Kenya, near the Somali border.

The United Nations says “massive” action is needed to save millions of people living in the Horn of Africa from starvation. U.N. and U.S. officials have said more than 11 million people are in need of emergency aid to survive.

A donors' conference will be held Wednesday in Kenya's capital, Nairobi. The U.N. is seeking pledges of $1.6 billion to help drought victims, many of whom are children.

On Tuesday, the U.N. refugee agency said tens of thousands of starving Somalis are fleeing their homes and coming to the capital, Mogadishu, in search of food and water.

The agency said 100,000 Somalis have arrived at Mogadishu-area camps in the past two months, and continue to come at a rate of 1,000 per day.

It says hundreds of thousands of others have fled to camps in neighboring Kenya and Ethiopia.

The U.N. formally declared a famine in two regions of southern Somalia last week. Access to southern Somalia has been hampered by the militant group al-Shabab, which controls large sections of the region and has denied that a famine is taking place.