"We have confirmed that nine people died in the attack by suspected LRA rebels," Radhia Achouri, spokeswoman for the UN Mission in Sudan, said. "We are investigating the incident."

The LRA, which has waged a war against the Ugandan government for 19 years, operates from bases in northern Uganda and southern Sudan. It is widely thought that the LRA's leader, the elusive Joseph Kony, ventures into Uganda to launch attacks on civilian targets then retreats to his southern Sudanese base.

"The LRA are active in southern Sudan, but it is very difficult to get to them, as this [southern Sudan] is a very vast and difficult terrain," Achouri said.

She noted, however, that with the signing of the Comprehensive Peace Agreement (CPA) between Khartoum and John Garang's southern Sudanese Liberation Movement/Army (SPLM/A), the effort to defeat the notoriously brutal rebel group would be much stronger.

"Now that the Sudan government, the SPL[M/]A and the Ugandan government are working together to defeat the LRA, we hope they can plan a strategy that will tackle the rebels in a decisive manner, but one that will not affect the CPA or the security in southern Sudan," Achouri said.

Meanwhile, the Ugandan army has said it killed seven LRA rebels on Monday in Kitgum district near the Uganda-Sudan border, as they attempted to cross over to Sudan.

"We intercepted a group destined for southern Sudan. They had supplies such as gum boots, which we believe they were taking to Kony in southern Sudan," Capt Paddy Ankunda, deputy spokesman for the Uganda People's Defence Forces, said on Wednesday from Gulu district in northern Uganda.

He said the army had rescued eight out of 12 civilians who were abducted in a weekend raid on Apala village in nearby Lira district. The rebels, he added, were still holding four abductees.

Frequent LRA attacks on southern Sudanese targets have, since January, forced at least 9,000 southern Sudanese to flee across the border to northwestern Uganda, according to UNHCR.