DAKAR, Senegal -- Ugandan rebels in eastern Congo have ruthlessly killed at least 620 people in the past month, and vulnerable civilians in the region desperately need protection, human rights groups said Saturday.

Human Rights Watch said many of the attacks carried out by Lord's Resistance Army rebels appeared to have been premeditated, and victims' skulls were crushed with wooden bats and axes.

Researchers from the New York-based organization gathered testimony and evidence on a two-week mission to the region with staff from the Congolese rights group Justice Plus.

They said that in one attack on Christmas Day in the village of Batande, rebels slaughtered the men and boys with blows to the head and raped women and girls in a nearby forest before killing them by crushing their skulls. Some 80 people died, they said.

"One of the few survivors, a 72-year-old man who arrived late for Christmas lunch, hid in the bushes and watched in horror as his wife, children and grandchildren were killed," Human Rights Watch said. The man said only six people survived.

After the massacre, the rebels "ate the Christmas feast the villagers had prepared, and then slept among the dead bodies before continuing on their trail of destruction and death" through another 12 villages.

In Faradje, about 150 miles from Batande, another group of rebels killed 143 people in a similarly gruesome attack in which they also abducted 160 children and 20 adults, tying them together and forcing them to carry looted goods. They also burned 940 houses, three primary schools and nine churches.

There were simultaneous Christmas attacks on several northeastern Congo villages near the Sudan border, Human Rights Watch said.

But it added in a statement that attacks are continuing.

Among the latest incidents of violence: 86 people massacred by rebels in Sambia, Akua and Tomate towns between Jan. 8 and Jan. 11.

"Hundreds of people have been slaughtered and this just goes on," said Joel Bisubu of Justice Plus. "We need food and medical supplies for the injured, but even more, we need protection."

The Catholic charity Caritas has said more than 400 people have been killed in the massacres and the U.N. has put the toll at around 500.

The Lord's Resistance Army has fought in northern Uganda for two decades, and rights groups have accused it of cutting off the lips of civilians and forcing thousands of children to serve as soldiers or sex slaves. The conflict has spilled into Sudan and Congo.

The latest attacks were apparently stirred up when Uganda's army, backed by Congolese and Sudanese soldiers, launched an operation Dec. 14 aimed at routing the rebels from Congo. They attacked the insurgents' headquarters in Garamba National Park, forcing them to flee. The rebels broke into several groups, "each of which targeted civilians along its path," Human Rights Watch said.

Rebel spokesman David Matsanga denied that the LRA killed hundreds.

"LRA forces are not in Congo. These people are combing an empty area," Matsanga said.

Human Rights Watch called on Uganda to do more to protect civilians.

"In the past, Ugandan army attacks on the LRA have often spurred immediate reprisals on civilians living nearby," Van Woudenberg said. "LRA atrocities like these show the Ugandan army needs to take steps to protect civilians when undertaking offensive military operations."

Ugandan Minister of Defense Ruth Nankabirwa said the attack on the LRA base had been successful and Ugandan forces now occupied all the LRA camps in Congo.

"We have captured some of the rebels. We got some of their documents so the operation is effective. The operation does not end in one day," she said.

The 18,000-strong U.N. mission in Congo is mandated to protect civilians, but its troops are mostly posted further south, around cities like Goma where separate fighting has taken place.

Long-running peace talks between the Lord's Resistance Army and Uganda's government have stalled.