In drought-ravaged Somalia where food is scarce, three-year-old Ibrahim is so severely malnourished he weighs less than eight kilos (18 pounds), about the same as an eight-month-old baby.

"My child is very sick, he's had a fever, vomiting and got diarrhoea," said his mother Rukyo Abdullahi, sitting worriedly by her tiny son's bedside, his skin stretched tight against his small bones.

"He was given some medicine from a local pharmacy, but as soon as he took it, he got worse -- the blood drained away from his face."

Abdullahi fled with Ibrahim into the famine-hit Somali capital last week, risking violence in one of the world's most dangerous cities in a desperate effort to save her son's life.

"I don't have any money to support my family," the tired looking mother added sadly, waving away the flies that buzz above her crying child.

She trekked some 50 kilometres (30 miles) on foot into the war-torn city with her feeble child, who also has measles.

Brought to Mogadishu's Banadir hospital, Ibrahim is struggling to survive. Too weak to eat, doctors are fitting him with a feeding tube through his nose.

Conflict-ridden Somalia is the hardest hit by an extreme drought affecting 12 million people across the Horn of Africa.

The United Nations has officially declared famine in Somalia for the first time this century, including in Mogadishu and four southern regions.

In the past two months, some 100,000 people have fled into Mogadishu, seeking food, water and shelter.

Hard working doctors are struggling to cope, offering what little they can with their basic facilities.

The UN's food monitoring unit has described Somalia as facing the most severe humanitarian crisis in the world and Africa's worst food security crisis since the country's 1991-1992 famine.

Doctor Lulu Mohamed, head of paediatrics at the hospital, said the situation is the worst she has seen since 1992.

That was the year after then president Siad Barre was toppled from power, and Somalia spiralled into the bloody conflict that has engulfed it ever since.

"Since then we haven't seen this overwhelming number of malnourished children -- and the death rate is increasing," Mohamed said.

Al-Qaeda-affiliated Shebab rebels, who had controlled around half of Mogadishu, abandoned their positions in a surprise withdrawal at the weekend.

But clashes have continued between rebel remnants and African Union-backed government troops.

There is some help in the city, but local aid workers say they are being overwhelmed by the demand.

"Day after day the situation is worsening because new arrivals are coming from drought affected areas to Mogadishu," said Adan Yusuf Mahadi, who helps run a feeding centre run by a local aid agency.

"People are in need, people need help," he said, warning that current relief efforts could in no way cope with the sheer number of people in need.

Outside the city, from where thousands continue to flee, the situation is reportedly worse, with aid agency access even more limited there.

"Where I am from, life is very difficult," said Abdullahi, who abandoned her family's farm after crops withered and animals died from the lack of rain.

"There is no aid getting there, we never get any help."