The ICC last week ordered the release of militia leader Lubanga, who is accused of enlisting child soldiers, because prosecutors were withholding evidence. But the court said he should remain in custody pending the appeal, which prosecutors filed on July 2.

The court said in a statement that Lubanga would remain in ICC custody until a final decision on the appeal is made.

"The reasons for the decision taken today by the judges will be given shortly by the appeals chamber," the court said.

Lubanga, who founded and led a militia in Congo's eastern Ituri district, was arrested in 2006 and is accused of enlisting and conscripting children under the age of 15 from 2002 to 2003. He has denied the charges.

The judges said last week they had given full consideration to the fears of Lubanga's alleged victims, who have warned that freeing the former warlord could ignite a "fire ball" in Congo's volatile Ituri region.

Experts estimate that a decade of violence in Congo has killed 5.4 million people, mainly through hunger and disease.

The trial of Lubanga had been due to start on June 23. The halt to proceedings was a major setback for the court, set up in 2002, which now has 106 member states and is also investigating crimes in Sudan, Uganda and the Central African Republic.

The court took custody last week of its highest-profile suspect to date -- Congolese former rebel warlord and vice-president Jean-Pierre Bemba, arrested in Belgium in May.

Bemba is accused of leading Congolese rebels who waged a campaign of rape and torture in the Central African Republic in 2002/2003.