KHARTOUM Sudan put 39 people on trial on Wednesday accused of taking part in a Darfur rebel attack on the capital last month.
Clashes, centred on a suburb of Khartoum, left at least 200 dead during the first attack on the city by a regional rebel group in decades of civil wars.
Three special courts tried 13 suspects each, drawing accusations from defence lawyers that they will not get a fair hearing.
The accused are being tried under Sudan's terrorism law and some could face the death penalty.
"These special courts are created by the chief justice, who is appointed by the president and cannot be neutral -- normal courts should be used," one member of the defence team, Kamal Omer, told Reuters.
The hearing was adjourned to give lawyers time to meet their clients. They had not previously had the chance to.
The May 10 attack on the western Omdurman suburb was carried out by the rebel Justice and Equality Movement.
Omer said none of the big names the government said had been caught, like senior commander Abdel Aziz el-Nur Ashr, were in court on Wednesday.
"They are all very young boys, many of them look like they could be between 15-18 years old."
Darfur's conflict began in early 2003 when mostly non-Arab rebels took up arms accusing central government of neglect. Khartoum mobilised mostly Arab militia to quell the revolt. Those militia now stand accused of war crimes.
International experts estimate some 200,000 people have died and 2.5 million been driven from their homes in Darfur.
The Darfur rebel Sudan Liberation Army Unity faction threatened on Wednesday to assassinate politicians in Khartoum over the trial of Darfuris by special courts. The group's commanders say they are now cooperating with JEM.
New York-based Human Rights Watch urged the government to release thousands of Darfuris arrested after the Khartoum attack or promptly charge them, saying they had spoken to people who described torture and beatings after being detained.
The former southern rebel Sudan People's Liberation Movement (SPLM), which joined government following a 2005 north-south peace deal to end a separate conflict, also called for an end to "arbitrary arrests of Darfuris".
The group had condemned the attack on Khartoum, which has made peace for Darfur look even more remote.
On Wednesday, the United Nations said some 1,000 armed militia had ridden through Geneina town, abducting and beating a U.N. staff member and holding three others at gunpoint.
"We are very concerned about what happened -- it is unacceptable for us. We don't want to be part of this conflict," said Noureddine Mezni, spokesman for the joint U.N.-African Union peacekeeping force (UNAMID). The UNAMID member was released after a government official intervened and is stable.
The militia had been fighting with Darfur rebels south of el-Geneina.
The UNAMID peacekeeping force, when fully deployed, should be the world's largest at 26,000 troops and police, but it has only around a third of its strength.
(Editing by Matthew Tostevin)