Over a million people in war-torn Somalia are struggling in conditions close to famine, with hunger and drought due to worsen, United Nations experts said Tuesday.

The grim assessment, based on the latest data collected by the UN, comes three years since famine in the Horn of Africa nation killed more than a quarter of a million people, and as heavy fighting persists in some of the hardest hit regions.

The UN said 1,025,000 people were classified in either "crisis" or "emergency" situations, just one step short of famine on its hunger scale. This represents an increase of a fifth compared with the numbers affected in January.

The joint report was released by the UN's Food Security and Nutrition Analysis Unit (FSNAU) and the US-funded Famine Early Warning Systems Network(FEWS NET).

"The gradual recovery and gains made since the end of the famine in 2012 are being lost as poor rains, conflict, trade disruptions and reduced humanitarian assistance led to a worsening of the food security situation," the statement said.

"Acute malnutrition increased in many parts of the country, particularly among children. The situation is likely to continue deteriorating further."

Over 43,000 children are at extreme risk of dying from hunger, while one in seven under five-year-olds -- some 218,000 children -- are acutely malnourished, it added.

More than 250,000 people, half of them children, died in the devastating 2011 famine.

Somalia's internationally-backed government, selected in 2012, was widely hailed as offering the best chance in decades to repair the war-ravaged country.

But reports of a hunger crisis even inside the capital casts a further pall over the government's record following accusations of corruption and continued attacks by Islamist Shebab insurgents in even the best-protected areas.

The hardline Shebab, which once controlled most of southern and central Somalia, has been driven out of positions in Mogadishu and Somalia's major towns by a 22,000-strong African Union (AU) force.

US air strikes on Monday reportedly targeted Shebab commanders, after AU and government forces launched a fresh offensive on Friday to seize key southern ports.

But while AU forces have captured towns, major roads connecting them are threatened by Shebab attacks, and food prices have soared.

"Access roads remain under insurgent control and trade flow is largely blocked, resulting in sharp increases in staple food prices," the statement added.