Famine-hit areas of southern Somalia will likely spread in coming days, with the situation continuing to worsen despite massive international aid efforts, the United Nations has warned.

"The situation in Somalia is deteriorating," the UN Office for the Coordination of Humanitarian Affairs (OCHA) said in a report released late Friday, noting that updated malnutrition figures will be "available shortly."

"The Somalia Food Security Nutrition Analysis Unit (FSNAU) warns...that almost all regions of the south could face famine," the report read.

"Although internal displacement is decreasing, rates of malnutrition and mortality are increasing and communicable diseases continue to spread," OCHA added.

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.

Famine was declared in the southern Bakool and Lower Shabelle regions of southern Somalia in July.

It later spread to three further areas, including into the Somali capital Mogadishu and the Afgoye corridor, the world's largest camp for displaced people.

Famine implies that at least 20 percent of households face extreme food shortages, acute malnutrition in over 30 percent of people, and two deaths per 10,000 people every day, according to UN definition.

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.

Al-Qaeda affiliated Shebab gunmen pulled out of positions in Mogadishu last month, but continue to restrict aid into areas they control in famine-hit southern regions.

Aid deliveries into the worst affected areas remains severely limited. The UN World Food Programme "only has partial access to the central areas and virtually none in the south," OCHA added.

Other aid agencies face similar difficulties, including the medical charity Doctors Without Borders (MSF).

"It is still proving extremely difficult to go beyond the gates of MSF's established health facilities to reach the most vulnerable people," a statement read.

"Despite repeated efforts and negotiations, we have still not been able to open new projects and develop new activities in southern Somalia," Alfonso Verdu, MSFs programme manager in Somalia said in a statement.

MSF, who have worked in Somalia throughout the past two decades of civil war, said poor security in Mogadishu had also limited aid efforts.

"The situation is extremely volatile and access to certain neighbourhoods is hindered by sporadic outbreaks of violence," MSF added.

A Malaysian cameraman was shot dead in Mogadishu on Friday and another journalist wounded when shooting broke out between African Union troops and other gunmen.

Meanwhile Somali leaders will hold a rare three-day conference in Mogadishu due to begin on Sunday in an effort to set up plans for a new government.

The current government is one of the more than a dozen attempts to form a central authority in Somalia since it plunged into war with the 1991 ouster of president Mohamed Siad Barre.