The agencies said two million people needed daily help to survive
Forty humanitarian agencies have warned of an impending catastrophe in Somalia unless urgent action is taken.
They say 20,000 people continue to flee violence in the capital every month.
The warning comes ahead of a UN Security Council meeting to consider sending 27,000 peacekeepers to Somalia to replace the stretched African force.
Correspondents say there are increasing attacks outside the capital, with Islamists raiding Jowhar town on Wednesday morning to release prisoners.
Residents told the BBC that hundreds of fighters, belonging to the Union of Islamic Courts (UIC), briefly held the town, about 90km (55 miles) north of the capital, Mogadishu, before pulling out after freeing the prisoners.
LIFE IN SOMALIA
2m rely on daily aid
More than 1m internally displaced
20,000 flee Mogadishu each month
Average monthly family income of those left in Mogadishu: $12.13
Life expectancy: 47
Problems: Fighting, high food prices, hyperinflation, drought
The BBC's Mohammed Olad Hassan in Mogadishu says five soldiers and two civilians were killed in the clashes.
Ethiopia intervened to help Somalia's interim government to oust the UIC from power in December 2006.
The agencies say two million Somalis need daily help to survive the crisis caused by continued fighting between insurgents and the government.
Somalia's ambassador to the UN said his government lacked enough international support and called for the partial lifting of the arms embargo
"It is ironic when the UN puts an arms embargo on a country which cannot secure its borders then anybody can import or export whatever they like and that's what was happening for 17 years," Elmi Ahmed Dualeh told the BBC.
"Now the government is weak. It is weak because it never had support."
In a joint statement, the 40 local and international aid agencies point out that in October last year they warned Somalia was heading towards crisis.
Six months on, they say, the situation in the country has deteriorated dramatically and access to those in need has got far worse.
"It continues to deteriorate by the day," the UN refugee agency's Guillermo Bettocchi told the BBC.
"There are no signs of improvement on the ground, and those who are suffering the brunt of the conflict are the civilians, who are being either killed or displaced, and are in the middle of suffering that is unacceptable," he said.
"In terms of child malnutrition, access to education, lack of access to clean water and sanitation facilities, indeed the situation in Somalia is the worst in the world... to be a child in Somalia today is something that means lots of suffering and a grim future."
Record food prices, hyper-inflation and drought in many parts of the country have made the situation worse and seasonal rains due to start soon are also predicted to fail.
"For too long, the needs of ordinary Somalis have been forgotten," the agencies said.
About 2,400 African Union peacekeepers have deployed so far
They urged "the international community and all parties to the conflict to urgently focus their attention on the catastrophic humanitarian crisis in Somalia".
"They must ensure access for humanitarian supplies, live up to their responsibility to protect civilians and address the environment of impunity," they added.
"The humanitarian crisis will become more and more complex and will continue to deepen in the absence of a political solution to the current crisis."
The UN Security Council will discuss the situation on Thursday.
Last week, UN Secretary General Ban Ki-moon presented the council with a report proposing the deployment of 27,000 peacekeepers as one of four possible scenarios in which the UN could heighten its presence in the war-torn country.
So far only 2,400 African Union peacekeepers have been sent to Somalia, of a planned 8,000-strong force.