Mediators in Burundi's peace process are investigating whether members of the country's last active rebel group, who have fallen out with their leader and expressed a willingness to join the process, were genuine combatants with the movement.

“We will not just sit and make an assessment and say that they are FNL combatants without testing," said the head of the mediation team, Charles Nqakula, who is also South Africa’s security minister.

The men say they fought for the Forces nationales de liberation (FNL) with Agathon Rwasa, but Rwasa's supporters have dismissed their claims and accused the government of creating a faction within the FNL.

The rebel group signed up to a ceasefire in September 2006 but the peace process remains stalled over their claim that Nqakula’s mediation is compromised by pro-government bias. FNL leaders did not attend the 21 October relaunch of the Joint Verification and Monitoring Mechanism. They had previously expressed doubts that their safety could be guaranteed if they travelled to the capital, Bujumbura.

"The mediation has an obligation to protect the FNL as well as those returning combatants," said Nqakula. "This is stated in the comprehensive ceasefire agreement. We will give all the leaders of the FNL all the security they require to ensure that nothing happens to them."

He said he would meet Rwasa whenever he was ready to participate in the peace process.

While fighting between the FNL and government forces is now rare, internal clashes have become more frequent. On the night of 21 October, seven FNL "dissident" fighters were killed when Rwasa's combatants attacked their position at Gakungwe in the western Kanyosha commune in Bujumbura Rural province, according to army spokesman Lieutenant Colonel Adolphe Manirakiza. Two government soldiers and two of the raiders also died in the attack. FNL spokesman Pasteur Habimana said his group was responsible for the assault.