PARIS — A UN court Wednesday increased the sentence of Radovan Karadzic, the former Bosnian Serb leader, from 40 years to life in prison for his role in the Bosnian war of the 1990s, reaffirming his conviction on charges of genocide, war crimes, and crimes against humanity.

Both the prosecution and the defense had appealed the 2016 result of Karadzic’s trial before the UN Criminal Tribunal for the Former Yugoslavia, in The Hague. Karadzic, who largely acted as his own lawyer in court, had asked to be acquitted of all charges.

The prosecution sought an increase in his sentence — a largely symbolic move, because Karadzic, 70 at the time of the verdict, was unlikely to live long enough to serve out his lengthy sentence. But symbolic or not, the court’s decision Wednesday to raise the penalty drew cheers and applause from Bosnians watching in the gallery.

The five-judge panel decided 3-2 that it was unreasonable for Karadzic to receive a 40-year sentence when some of his subordinates had been sentenced to life for their roles in the same atrocities, particularly the July 1995 massacre in and around the town of Srebrenica. The defendant watched calmly as the decision was delivered.

Prosecutors had asked the court for an additional genocide verdict in the case, based on events in seven Bosnian towns where tens of thousands of people were killed, but the panel rejected that request, which had been the subject of intense debate among lawyers, human rights groups, and victims.

During the war, which raged from 1992 to 1995, Karadzic was president of Republika Srpska, the region that tried to break away from Bosnia, where violence carried out by the dominant Serbs forced out much of the Croat and Muslim population.

His trial, followed by the three years of appeals, was the most important in the 23-year history of the UN tribunal and was widely seen as a test of whether the modern international criminal justice system could impose accountability on wartime leaders.

The proceedings thoroughly investigated the bloodiest conflict in Europe since World War II, which tore apart Yugoslavia, ravaged several of the smaller nations that emerged from it and left more than 100,000 people dead.

Among the Balkan combatants — Serbia, Bosnia, Kosovo, and Croatia — millions of people were displaced, many of them forced from their homes in campaigns of ethnic cleansing.

“The measure of success or failure of this verdict will not be in where Radovan Karadzic makes his residence between now and his death, or in what a gaggle of self-seeking politicians will do in the next week or month,’’ said Eric Gordy, professor at the School of Slavonic and East European Studies at University College London.

“What will matter about the verdicts will be the documentary record that they establish,’’ he said.