Bahr Idriss Abu Garda has now formed his own rebel group
A Darfur rebel charged with war crimes has appeared before the International Criminal Court (ICC) in The Hague.
Bahr Idriss Abu Garda is charged with taking part in an attack in north Darfur in 2007, during which 12 African Union (AU) peacekeepers were killed.
Mr Abu Garda, 46, is the first person from the Darfur conflict to appear before the ICC. He denies the charges.
Sudanese officials, including the president, have been accused of war crimes but have not gone to The Hague.
Mr Abu Garda handed himself in to the court on Sunday.
"The court appreciates very much your volunteer appearance," Judge Cuno Tarfusser told him at the start of proceedings, reports the AFP news agency.
"You have sent out a very good message."
The United Nations estimates that 300,000 people have died in a six-year conflict in Sudan's Darfur region and more than two million more have been displaced.
Mr Abu Garda, wearing a grey suit, told the court he understood the charges, according to the AP news agency.
He is charged with three war crimes allegedly committed during the assault on the Haskanita AU camp in September 2007.
ICC chief prosecutor Luis Moreno-Ocampo has called the incident "the most serious attack against peacekeepers in Darfur".
A spokesman for Mr Abu Garda's United Resistance Movement (URF) rebel group told the BBC's Focus on Africa programme that he was happy with the process.
"We are here in respect of international law and in respect of those who lost their lives in Haskanita," said Tadjadine Bashir Niam, who was in court.
"We believe he is innocent. We will co-operate with the African Union, the court and others to find out the real killers."
Mr Niam said that Mr Abu Garda was the victim of differences between the Justice and Equality Movement (Jem) rebels - the group he left to set up the URF. Jem has said it helped collect evidence against him.
No arrest warrant was issued as Mr Abu Garda had shown a willingness to appear before the ICC, prosecutors said.
In March, Sudan's President Omar al-Bashir was indicted on war crime charges, which were the first issued by the ICC against a sitting president.
In a BBC interview earlier this month, President Bashir dismissed the charges as propaganda.
The ICC has also issued indictments for two other senior Sudanese officials over the Darfur conflict.
Black African rebel groups took up arms in 2003, accusing the government of ignoring the region.
The government denies accusations that it then mobilised Arab militias to take revenge on the local population, in what the US and others have called a genocide.