KINSHASA: Ugandan LRA rebels killed at least 321 civilians in a previously unreported "well-planned" four-day attack on villages in the DR Congo last December, Human Rights Watch said Sunday.

In a report released in Kampala, HRW said 250 others, including at least 80 children, were abducted in the December 14-17 Lord's Resistance Army attack in the remote Makombo area of northeastern Haut Uele district.

A Catholic clergyman at Isiro-Niangara in the same district, speaking before the report was issued, confirmed that 30 members of the rebel LRA attacked a dozen villages of Haut Uele, which is in Orientale province.

"They killed at least 300 people. They also kidnapped between 200 and 400 others before disappearing," clergyman Dieudonne Abakuba told AFP.

"During the well-planned LRA attack," the rebel outfit "killed at least 321 civilians and abducted 250 others, including at least 80 children," said the HRW report headed "Trail of Death: LRA Atrocities in Northeastern Congo."

"The vast majority of those killed were adult men, whom LRA combatants first tied up and then hacked to death with machetes or crushed their skulls with axes and heavy wooden sticks.

"The dead include at least 13 women and 23 children, the youngest a three-year-old girl who was burned to death. LRA combatants tied some of the victims to trees before crushing their skulls with axes," said the report, written after a mission visited the region in February.

Between 25 and 40 rebels had walked for 100 kilometres (65 miles) during the operation which was aimed at killing, abducting and pillaging, Human Rights Watch said.

"The Makombo massacre is one of the worst ever committed by the LRA in its bloody 23-year history, yet it has gone unreported for months," said Anneke Van Woudenberg, a senior Africa researcher for the rights watchdog.

"The four-day rampage demonstrates that the LRA remains a serious threat to civilians and is not a spent force, as the Ugandan and Congolese governments claim."

Human Rights Watch said witnesses it interviewed said that "for days and weeks after the attack, this vast area was filled with the 'stench of death.'"

Children and adults who escaped gave similar accounts of the "extreme brutality", it said.

"Many of the children captured by the LRA were forced to kill other children who had disobeyed the LRA?s rules.

"In numerous cases documented by Human Rights Watch, children were ordered to surround the victim in a circle and take turns beating the child on the head with a large wooden stick until the child died," the report said.

The clergyman said the rebels were wearing military uniforms. "They killed a lot of people on the road and attacked them with bludgeons," he said.

"They killed mainly men. They chopped some people's heads off and kidnapped children on their way to school," added regional lawmaker Jeannette Abakuba, confirming the more than 300 dead.

The villages that were raided are south of the Uele river, 40 kilometres (25 miles) southwest of the town of Niangara, and include Mabanga, Makombo, Ngbiribi, Tapili and Kiliwa.

Some people fled and were slowly coming back.

"But the atmosphere is poisoned, people are scared the LRA might come back, they're afraid of farming, so there's a risk of famine," said the clergyman.

Led by Joseph Kony, wanted along with two other leaders by the International Criminal Court for war crimes, the LRA took up arms in 1988 in northern Uganda and has acquired a reputation for brutality.

Since 2005, under pressure from the Ugandan army, the fighters pulled back from their bases in Uganda to move into the remote northeast of the DRC, where they were said to number fewer than 100 late last year, according to the UN mission in the DRC.