(CNN) Former Bosnian Serb leader Radovan Karadzic's sentence for genocide has been increased by appeal judges at a UN court in the Hague, Netherlands, from 40 years to life imprisonment.

In 2016, the International Criminal Tribunal for the former Yugoslavia sentenced Karadzic to 40 years in prison for genocide over the 1995 Srebrenica massacre -- in which more than 7,000 Bosnian Muslim men and boys were executed by Bosnian Serb forces under his command -- as well as other crimes, such as persecution, extermination, murder, deportation, inhumane acts, terror, unlawful attacks on civilians and hostage-taking.

Judge Vagn Joensen said the original sentence did not reflect the "gravity" of Karadzic's crimes, and "his responsibility for the largest and gravest set of crimes ever attributed to a single person at the ICTY."

Karadzic pictured at the start of his trial in 2008, left, and in his disguise, right

"Taking into account the Trial Chamber's conclusions reflecting the magnitude of Karadzic's crimes, the Appeals Chamber is in agreement with the Prosecution's position and considers that the 40-year sentence inadequately reflects the extraordinary gravity of Karadzic's crimes as well as his central and instrumental participation in four joint criminal enterprises," said the judge.

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"Given the above, the Appeals Chamber considers that the sentence of 40 years imposed by the Trial Chamber underestimates the extraordinary gravity of Karadzic's responsibility and his integral participation in 'the most egregious of crimes' that were committed throughout the entire period of the conflict in Bosnia and Herzegovina and were noted for their 'sheer scale' and 'systematic cruelty,'" added Joensen.

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