The leader of a breakaway faction of Darfur's main rebel and his deputy have been killed after an attack inside Chad near the border with Sudan.
Mohamed Bashar and Suleiman Arko were killed during fighting with the Justice and Equality Movement (JEM), Sudan's intelligence agency announced on Sunday.
JEM fighters aboard a 30-vehicle convoy reportedly attacked Bashar's group while they were having lunch, just a few kilometres from the Sudanese border, Al Jazeera's Harriet Martin, reporting from Khartoum, said.
Martin said that there had been conflicting reports about which side started the fight.
Nahar Osman, an adviser of Bashar, said that his group was attacked.
In an interview with the Sudan Tribune, Nahar said that five other members of Bashar's group were killed, along with a Chadian security officer and two cattle keepers working nearby.
JEM said Bashar's forces attacked its base forcing them to fight back. Al Jazeera's Azhar Sukri said that the main body of JEM rebels appears to have been angry with Bashar for co-operating with the Sudanese government.
Bashar's rebel faction had signed a peace deal in Doha on April 6 with the Sudanese government to halt 10 years of fighting in Darfur. His top aide Arko led the negotiating team.
It was founded by Darfuris, loyal to a prominent religious and political leader Hassan al Turabi.
Blow to peace process
Martin said: "His [Bashar's] death and the death of his deputy is very significant," Martin said, adding that was a serious blow to the peace process.
She said that the main JEM group may not have "forgiven" Bashar for signing-up to the Darfur peace deal.
Last April, JEM fighters killed a deputy commander of the breakaway faction allied with Bashar.
Salah Eddin Elzein, director of Al Jazeera's Centre for Studies, said that Bashar's death could also raise serious questions about the security arrangement between Sudan and Chad.
"If this happened within Chad, it is a serious development," Elzein said, adding that both countries have troops patrolling the border.
Elzein also said that the killing of Bashar dealt a blow to the "piecemeal" approach of the African Union in Darfur.
The death of the two top rebel leaders will also put on hold the peace agrement already signed in Doha by the rebels and the government of Sudan, he said.