The International Criminal Court on Wednesday convicted Congolese militia chief Thomas Lubanga of war crimes for conscripting children into his rebel army, the tribunal's first ever verdict.

Lubanga, 51, was found guilty in The Hague of abducting children as young as 11 and forcing them to fight and commit atrocities in a bloody war in a gold-rich region of the Democratic Republic of Congo (DRC).

Rights groups hailed the judgment, saying it sent a strong message to those who force young children to kill -- including Ugandan rebel leader Joseph Kony, now the target of an international online activist campaign.

"Today's verdict will give pause to those around the world who commit the horrific crime of using and abusing children, both on and off the battlefield," said Amnesty International's Michael Bochenek.

Hollywood star Angelina Jolie, who is funding a public information campaign in the DRC about the trial, witnessed the verdict in court and said she hoped it would "provide some measure of comfort for the victims".

"It sends a strong message against the use of child soldiers," the actress, director and rights activist added in a statement after watching proceedings from the front row of the public gallery.

A decade after the ICC was launched, presiding Judge Adrian Fulford read its first verdict, finding Lubanga was guilty of "conscription and enlisting children under the age of 15 and used them to participate in hostilities".

Prosecutors told the court that militia under Lubanga's control had abducted children as young as 11 from homes, schools and football fields to serve as soldiers, and that young girls were used as sex slaves.

In closing arguments last year, one prosecutor, Fatou Bensouda, told the court child soldiers were "used to rape and pillage" and said: "Those who have no visible scars on their body keep the scars that will remain within."

Lubanga -- thought to be the founder of the Union of Congolese Patriots (UPC), and chief commander of its military wing -- was sent to The Hague in 2006 and put on trial in early 2009.

The warlord, who has denied the charges against him, will be sentenced at a date yet to be determined, the court said.

He could face 30 years in jail or, if judges decide the crimes were exceptionally grave, life in prison. Lubanga will remain behind bars at the ICC detention facility in the nearby suburb of Scheveningen.

Human Rights Watch's international justice officer Geraldine Mattioli told AFP the conviction is "a sign that impunity does not exist any longer".

Alpha Sesay, international legal officer at the Open Society's Justice Initiative, said the ruling would send a strong message to others who used child soldiers, including Uganda's Kony.

Kony, leader of the rebel Lord's Resistance Army, has been the subject of an intense online campaign this month to bring him to justice for war crimes and crimes against humanity.

"This judgment will have an effect in Ituri (in the DRC). It will have the same effect in Uganda," Sesay said.

During the trial Lubanga's lawyers accused the prosecution of fabricating evidence with the help of intermediaries used to find witnesses and claimed that individuals were paid to give false testimony.

Judge Fulford rapped the prosecution team, saying it had failed in some instances to verify testimony organised through intermediaries.

"The prosecution should not have delegated its investigative responsibilities to the intermediaries," the judge said, adding that chief prosecutor Luis Moreno-Ocampo "should ensure that the risk of a conflict of interest is avoided".

Moreno-Ocampo was to make a statement Thursday on the case.

During 204 days of hearings, prosecutors called 36 witnesses, the defence 24, and three testified for victims.

The ICC has issued four arrest warrants for crimes in the DRC and is investigating seven cases, all in Africa.

Two militia leaders, Germain Katanga, 33, and Mathieu Ngudjolo Chui, 41, who fought against Lubanga, are now facing trial on similar charges.

Former UPC chief Bosco Ntaganda, a Lubanga ally, is yet to be arrested to face the court on war crimes charges.

(Congolese former rebel commander Thomas Lubanga listens to the verdict in his war crimes trial at the International Criminal Court in the Hague on Wednesday. He was found guilty of using children in his rebel army, in the tribunal's first ever verdict. AFP Photo/Evert Jan Daniels)