"Since June 2002, the LRA has abducted approximately 8,400 children, resumed its despicable practice of mutilating people it believes to be affiliated with the government and targeted religious leaders, aid providers and other civilians," it said.
The LRA's 17-year war against the army in northern Uganda has been characterised by great brutality.
The LRA is led by self-proclaimed prophet Joseph Kony, said to take his orders from the Holy Spirit, which takes possession of his body. His force is made up mainly of children, thousands of whom have been abducted.
Kony has said he wants to overthrow the government and rule Uganda by the biblical Ten Commandments.
Operation Iron Fist failed
|Laura Bush with Ugandan children|
In March 2002, Ugandan President Yoweri Museveni's army launched an unsuccessful military offensive to flush out the rebels from their bases in southern Sudan.
"Operation Iron Fist had a boomerang effect in that the LRA, instead of being wiped out, evaded the UPDF in Sudan and returned to northern Uganda in June 2002 with new equipment, uniforms and training," the report by four groups including New York-based Human Rights Watch said.
The 73-page report also accuses the Uganda People's Defence Force of rights abuses in the region, including torture, rape, summary executions and recruiting underage soldiers.
Civilians are destitute and desperate. An estimated 800,000 people -- or 70 percent of the population in the three war-affected districts -- have fled their homes, many ordered to move to "protected" camps by the government.
Fear of abduction has driven some 20,000 children into the town of Gulu every night, where they sleep on verandas, church grounds and hospitals before going home each morning, says the report.
LRA abductees are threatened with death if they try to run away. Children are forced to beat, club or trample to death other children or adults who attempt to escape.
One 13-year-old boy who did get away recounted how rebels tied up two of his five brothers and made the others watch.
"They beat them with sticks until the two of them died," he said. "They told us it would give us strength to fight. My youngest brother was nine years old."