BBC News 10 July 2012 Last updated at 07:05 ET
Judge Adrian Fulford said Lubanga would effectively spend eight more years behind bars.
Congolese warlord Thomas Lubanga has been sentenced to 14 years in jail for recruiting and using child soldiers in his rebel army in 2002 and 2003.
Taking into account time in custody, he will now serve a further eight years.
In March, he became the first person to be convicted by the International Criminal Court (ICC) since it was set up 10 years ago.
The conflict between ethnic groups in Ituri, north-eastern DR Congo, is estimated to have killed 60,000 people.
Lubanga led the Union of Congolese Patriots, an ethnic Hema militia which was active in the war that started in the Ituri region and its main town of Bunia in 1999.
This was a local conflict within the wider DR Congo war, which left an estimated five million people dead - mostly from hunger and disease.
The Lubanga case is closely related to the current fighting in DR Congo, where forces loyal to Gen Bosco Ntaganda are threatening the main eastern city of Goma.
Gen Ntaganda is accused of the same crimes as his erstwhile ally Lubanga and his M23 group resumed its rebellion shortly after Lubanga was convicted, amid mounting calls for Gen Ntaganda to be arrested.
During the trial, the court heard how Lubanga would go to people's homes and ask them to donate something for the war effort. He would ask for cash, a cow, or for a child to fight for his rebel army.
The court also saw video footage of Lubanga at a training camp, galvanising children as young as 10.
Another video showed young children working as bodyguards.
Lubanga was arrested in March 2005 by UN peacekeepers, along with other militiamen.
He showed no emotion as he was sentenced.
He cried as he was transferred to The Hague in March 2006.
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