A UN relief team was due in northern Lira district on Tuesday to determine whether aid workers could travel there safely to assess needs, UN officials said in New York.
The World Food Programme was standing by with food supplies while the Ugandan Red Cross Society and other aid groups were preparing to provide shelter, the officials said.
Local authorities said the Lord's Resistance Army rebels attacked the camp of 4800 homeless Ugandans on Saturday evening with automatic weapons and hand grenades.
They then set fire to grass-thatched huts in which people were hiding. Victims were found burned, shot, bludgeoned or hacked to death, the United Nations said.
The survivors managed to escape by fleeing into the bush and were being relocated in the town of Lira and other nearby areas.
Lira district already houses 120,000 people driven from their homes due to the long conflict in northern and eastern Uganda, where the Lord's Resistance Army has defied repeated attempts by the army to crush its 17-year insurgency.
The UN team on its way to Lira included officials from the Office for the Coordination of Humanitarian Affairs and the children's agency UNICEF.
UN Secretary-General Kofi Annan issued a statement calling the killing spree a "senseless massacre" and appealing "to all those at the national and international level who are in a position to stop the terrible cycle of violence in northern Uganda to do their utmost to protect innocent civilians".
The LRA attacked the camp with
rifles and grenades
UN officials said they were stepping up humanitarian efforts in the region, which they say is the world's largest neglected humanitarian emergency.
The LRA says it is fighting to defend the rights of the northern Acholi people, but has never made a detailed public statement of its demands.
The movement, led by self-proclaimed mystic and former altar boy Joseph Kony, has abducted an estimated 30,000 children for use as fighters and sex slaves since the mid-1990s.
Meanwhile, the International Criminal Court (ICC) - the world's first permanent war crimes court - has said it will investigate the weekend massacre.
ICC spokeswoman Claudia Perdomo said it would be a "preliminary investigation", during which the war crimes prosecutor would gather information from the region to see if there was enough to launch a legal probe.
The ICC, which became a legal reality in July 2003, is the permanent tribunal mandated to try war crimes, crimes against humanity and genocide.