The International Criminal Court has found Congolese warlord Thomas Lubanga Dyilo guilty of war crimes in its landmark first ruling since it was set up a decade ago.
Lubanga was accused of recruiting and deploying child soldiers during a five-year conflict until 2003.
"The chamber reached its decision unanimously that the prosecution has proved Thomas Lubanga guilty of crimes of conscription and enlisting children under the age of 15 and used them to participate in hostilities," presiding Judge Adrian Fulford told the Hague-based court.
Humanitarian NGOs said at least 60,000 people were killed from 1999 to 2003 when the war ended.
Lubanga, 51, faced two counts of conscripting and enlisting child soldiers under the age of 15 to fight for his militia during the four-year war in the remote northeastern Democratic Republic of Congo's Ituri region.
First transferred to The Hague in 2006, the alleged founder of the Union of Congolese Patriots and chief commander of its military wing went on trial in January 2009.
Arguments closed in August last year.
Prosecutors alleged that Lubanga's role in the conflict was driven by a desire to maintain and expand his control over Ituri, one of the world's most lucrative gold-mining territories.
He had pleaded not guilty to the charges.
Prosecutors alleged that the Patriotic Forces for the Liberation of Congo militia under Lubanga's control abducted children as young as 11 from their homes, schools and football fields.
They were taken to military training camps, where they were beaten and drugged.
Girls among them were used as sex slaves, prosecutors told the court.
During 204 days of hearings, prosecutors called 36 witnesses, the defence called 24, and three represented victims.
Lubanga could face up to life imprisonment, although a sentence will not be passed immediately. An appeal can be filed within 30 days.
The ICC, the world's only independent, permanent tribunal to try genocide, war crimes and crimes against humanity, has issued four arrest warrants for crimes in the DRC since opening its doors in 2003 and is investigating seven cases, all based in Africa.
International reaction
In the Congolese capital Kinshasa, Sharanjeet Parmar of the International Centre for Transitional Justice said: "The result is important... for the DRC in terms of fighting the culture of impunity, because very few people who're accused of war crimes are brought to justice."
Mr Parmar added that local people were now eager to see some form of reparation made for their suffering.
They also wanted Bosco Ntaganda, a general indicted along with Lubanga, to be handed over to the ICC, he said.
Amnesty International said: "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."
However, it noted that the use of child soldiers continued.
It also urged speedier trials at The Hague, and was critical of the fact that the court did not pursue allegations of other crimes committed under Lubanga, including rape.
UN rights chief Navi Pillay called the verdict "a great step forward for international justice and a major milestone in the fight against impunity".
While US State Department spokeswoman Victoria Nuland told reporters that it was "an historic moment and an important step in providing justice and accountability to the Congolese people."
