The trial of Thomas Lubanga at the world's first permanent war crimes court had been due to start in March, but Lubanga's lawyers said prosecutors had not disclosed all the evidence as stipulated by the court.

A court spokeswoman said on Thursday that judges will now set a new date by which time prosecutors must disclose all evidence to the defence, with the trial expected to start three months after that.

During a hearing on Wednesday judges mentioned a tentative start date of June.

Lubanga, who founded and led a militia in the Democratic Republic of Congo's Ituri district, was arrested in 2006 and accused of enlisting and conscripting children under the age of 15 to kill members of the Lendu ethnic group during the country's 1998-2003 war.

Lubanga has denied the charges.

The ICC ruled in January 2006 that there was enough evidence to try Lubanga, a milestone for the institution that was set up in 2002 and is now backed by 105 nations.

Lubanga led the Union of Congolese Patriots (UPC), an ethnic militia now registered as a political party, and is accused of using children to kill his enemies in the ethnic conflict in Ituri between the Hema and Lendu, and in clashes between militia groups vying for control of mines and tax revenues.

The ICC is also in the early stages of prosecuting Germain Katanga, another Congolese militia leader, who is accused of murder, sexual slavery and also using child soldiers.

A third suspect, former Congo warlord Mathieu Ngudjolo, was surrendered to the court last week, where he faces war crimes charges of murder, sexual slavery and using child soldiers.

Ngudjolo's arrest comes as the government of President Joseph Kabila is attempting to bring to an end a decade of violence in Congo that experts estimate has killed 5.4 million people, mainly through hunger and disease.