African leaders will meet Thursday to pledge funds to tackle the famine in Somalia and extreme drought across the Horn of Africa which are putting millions of people at risk of starvation.

African Union Commission chairman Jean Ping will appeal to the continents' leaders and the international community to assist more than 12 million drought-hit people in the region, during a pledging conference in the Ethiopian capital.

"(I) wish to make this clarion call to all Africans to... act out against hunger by providing both cash and in-kind support for urgent life-saving assistance to our brothers and sisters in the Horn of Africa," Ping said in a statement.

Some 12.4 million people in the Horn of Africa, including parts of Ethiopia, Djibouti, Kenya and Uganda, are affected by the worst drought in decades in the region and are in need of humanitarian assistance, according to the UN.

The demands are huge, with a $1.1 billion shortfall from a total $2.4 billion needed, according to UN Office for the Coordination of Humanitarian Affairs (OCHA).

Somalia is the worst hit, with several southern regions in famine, where more than 390,000 children are at risk of dying from malnutrition, according to OCHA.

The UN has described Somalia, where a civil war has been going on since 1991, as facing the most severe humanitarian crisis in the world.

The conference will be attended by the AU representative to Somalia and former Ghanaian president, Jerry Rawlings, as well as the deputy secretary general of the United Nations, Asha Rose Migiro, AU spokesperson Nabo Sene told AFP.

"African countries should be proactive in addressing the drought situation in the affected states," the AU said in a statement.

The conference will give a "concrete expression of solidarity" from other African nations and the drought-hit regions, it added.

Also expected to attend are leaders of African economic blocs and heads of state from East Africa's Intergovernmental Authority on Development, which includes Uganda, Kenya, Djibouti, Sudan, Ethiopia and Somalia.

But a pan-African fundraising campaign, Africans Act 4 Africa, has criticised African governments and the AU for not responding quickly enough to the crisis.

"The overall international donor response to this humanitarian crisis has been slow and inadequate," the organisation said in a statement.

"Contributions (have been) too modest to decisively change the conditions for the millions who need this support."

Organisers of the campaign said the African community should offer a minimum of $50 million to relief efforts. The African Union has so far pledged $500,000.

"This was a preventable catastrophe. It is an extreme example of our broken food system. Droughts may be inevitable in this region, but disasters are not," the coalition of civil society groups that make up the fundraising campaign added.

"Decades of marginalisation, neglect and under-investment in pastoralists and smallholder food producers, many of them women, have contributed to the current crisis."

Last week the Organisation of Islamic Cooperation pledged $350 million to assist drought-struck Somalis.

Ping was in Mogadishu last Saturday, where he met with famine victims and called for a strengthening of the Djibouti Accord and the Kampala Accord, which call for peace in the country.

Relief agencies have boosted aid delivery to the affected population, but insecurity in one of the world's most dangerous countries is hobbling a wider reach.

Last week Turkish Prime Minister Recep Tayyip Erdogan toured Mogadishu on the first visit to the war-torn city by a major leader in almost 20 years, calling the situation in Somalia "a problem for all humanity".