MOGADISHU - The UN's top humanitarian official appealed for more help for Somalia on Monday as an insurgency that has killed thousands of civilians this year brought fresh bloodshed in the capital.

John Holmes, the UN undersecretary general for humanitarian affairs, said aid agencies are struggling to operate because of violence in this Horn of Africa nation, which the UN says faces Africa's biggest humanitarian crisis.

"There is a (humanitarian) response but it is not adequate. It is terrible over here,'' Holmes told reporters after landing about 50 kilometres southwest of the capital, Mogadishu.

He visited a feeding centre just west of Mogadishu, where many of the thousands of Somalis fleeing the fighting were seeking help.

At the centre, Shamsa Ahmed said her two-year-old daughter was "severely malnourished. I don't think she will survive. I'm just waiting for her to die.''

In the capital, mortar shells slammed into a residential area. Dahir Moalim Khasim, a neighbourhood resident, said he had seen the bodies of two civilians.

Holmes was scheduled to meet President Abdullahi Yusuf and new Prime Minister Nur Hassan Hussein during his one-day visit. On Sunday, Hussein said he would try to open a dialogue with Islamic extremists to end the fighting. Numerous such attempts have so far failed.

Ethiopia came to the aid of Somalia's government last December to rout the Council of Islamic Courts militia. The Islamic group's fighters have since launched an Iraq-style insurgency, and gunbattles, grenade and mortar attacks have devastated this seaside capital.

Somalia has not had a functioning government since warlords overthrew a dictator in 1991, then turned on one another.

African Union peacekeepers have failed to stop the violence. Holmes said a UN peacekeeping mission could only succeed where there is peace to keep.

In August, the UN Security Council called on the UN secretary general to begin planning for possible peacekeeper deployment. But Secretary General Ban Ki-moon opposes a UN deployment, suggesting instead that a robust multinational force or a coalition of volunteer nations help restore security.

More than a decade ago, a massive UN relief operation was launched for thousands of civilians left starving because of fighting in Somalia. But 1993 attacks by Somali militiamen that brought down two Black Hawk helicopters and killed 18 U.S. servicemen were followed by the withdrawal of U.S. troops and the eventual end of the UN peacekeeping operation.

The UN World Food Program said Monday the number of people it had been providing daily meals in Mogadishu has hit 21,000, and it aimed to reach up to 50,000.

New York-based Human Rights Watch urged the UN Security Council to press Ethiopia and Somalia to stop "grave human rights abuses'' fueling the humanitarian crises in Somalia and in Ethiopia's ethnically Somali Ogaden region.