The four members of the tribal Mai-Mai militia were convicted for their role in the "assassination" of three Indian UN troops last August, Captain Bernard Kangela, military prosecutor of the court in Goma, said.

The court in Nord-Kivu province acquitted four other militia members citing lack of evidence.

Three Indian UN soldiers were hacked to death and seven wounded during a surprise attack by 60 Mai-Mai militia on a UN base in Nord-Kivu at Kirumba, 30 kilometres (about 20 miles) south of Rwindi.

Court president Major Rene Zingi said that the Mai-Mai member sentenced to death denied the charges but added that "the others identified him as their leader."

He added that the UN mission in the DR Congo MONUSCO was not acting as a plaintiff in the case.

Although courts issue death penalties in the country, no executions have taken place since President Joseph Kabila came to power in 2001.

The Mai-Mai are local clan militias that changed sides in successive wars that wracked the DR Congo between 1997 and 2003. They have remained under arms and remain one of the sources of instability in the east.

Most Mai-Mai groups consider themselves to be local defence militias. They believe in witchcraft and before going into battle drink special potions that they believe will protect them from harm.

In some parts of Nord-Kivu and Sud-Kivu provinces, the Mai-Mai have become allied to Hutu rebels of the Democratic Forces for the Liberation of Rwanda (FDLR), and Kinshasa's troops have been hunting both since early 2009.

Eastern DRC has been wracked by instability for more than a decade due to the presence of armed groups which routinely carry out widespread looting, murders and rape of hundreds of women and children.

MONUSCO, earlier known by its French acronym MONUC, has been present in DRC since late 1999 and its new mandate to consolidate peace runs out at the end of the month.

"We're are waiting for Mbeki to come back from Sudan. He flew to Sudan today early this morning," south Sudan's cooperation minister Deng Alor told journalists.

He said Mbeki, the former South African president, had planned to go to north Sudan's only oil producing state, South Kordofan.

There was no official confirmation of the visit from Mbeki's aides or from the African Union.

The talks in Addis Ababa have been going on behind closed doors alternately at the African Union (AU) headquarters, the Ethiopian presidential palace and the Sheraton hotel since Sunday

Diplomats attending the meeting said the two parties were not meeting together, but rather each side separately with members of the AU mediation team.

Each side is deliberating on proposals put forward by the AU, but chief mediator Thabo Mebki has instructed delegates they should not talk to the press before the talks wrap up.

No "significant progress" has been made, according to a diplomat at the AU.

Just one month ahead of full independence for the south, crises have flared ip in two border flashpoints: Abyei, occupied by the northern army since May 21 in retaliation for an attack on a convoy, and South Kordofan.

Heavy fighting has raged there since June 5, pitting the northern army and allied militiamen against troops aligned to southern former rebel group the Sudan People's Liberation Army (SPLA).

In Kartoum meanwhile the northern army said it would use all available to means to supress what is calls "the rebellion" in South Kordofan.

"Until this moment we are continuing our operations in the hills around Kadugli, to stop this rebellion... We will continue to fight by all the means we have," Sawarmi Khaled Saad told a news conference in Khartoum, referring to the South Kordofan capital.

World leaders including US President Barack Obama and UN chief Ban Ki-moon have called for an immediate ceasefire.

The conflict has so far caused more than 60,000 people to flee their homes, according to UN estimates, with the UK-based charity Save the Children saying on Thursday that 30,000 of those displaced were children.

The army spokesman dismissed claims that it was aggravating the humanitarian situation, instead blaming the state's former deputy governor, Abdelaziz al-Hilu, himself a senior SPLA commander, for starting the rebellion.

"Our role is to protect the civilian population and we have carried out these operations to protect the civilians and the roads in South Kordofan," he said.