Record high food prices, hyper-inflation and drought across the Horn of Africa nation were exacerbating the situation and will worsen if seasonal rains due from April fail as predicted.

"The crisis engulfing Somalia has deteriorated dramatically while access to people in need continues to decrease," the agencies said, citing attacks on aid workers and looting of supplies.

Foreign aid workers are increasingly frustrated at the lack of attention to Somalia, which has suffered 17 years of near-incessant conflict since warlords toppled former military ruler Mohamed Siad Barre.

In Africa, the conflict in Sudan's Darfur region has overshadowed Somalia, even though some UN officials say the humanitarian situation may be worse in Somalia.

"For too long, the needs of ordinary Somalis have been forgotten," the agencies added.

"(We) ask the international community and all parties to the conflict to urgently focus their attention on the catastrophic humanitarian crisis in Somalia."

The 250,000 people camped in a small corridor between Mogadishu and Afgoye to the west are now considered the largest group of internally displaced people in the world, the statement said.

"According to (UN children's agency) UNICEF Somalia is the worst place in the world for children. Approximately one in seven children under the age of five in Somalia are acutely malnourished," it added.

(Reporting by Lisa Ntungicimpaye, Editing by Andrew Cawthorne and Jon Boyle)