Ratko Mladic, the former Bosnian Serb general charged with orchestrating the largest mass killing of civilians in Europe since World War II, was arrested Thursday in Serbia, ending a nearly 16-year manhunt that stood as a test of the West’s commitment to hold accused war criminals accountable.

Mladic, 69, was indicted twice, first in 1995 by the International Criminal Tribunal for the former Yugoslavia, on more than a dozen counts of genocide, war crimes and crimes against humanity during Bosnia’s 1992-95 war. He was charged with commanding troops responsible for enforcing the 46-month siege of Sarajevo and for slaughtering about 8,000 Bosnian Muslims near the town of Srebrenica in July 1995.

After Thursday’s arrest, Serbian President Boris Tadic told reporters in Belgrade that Mladic was picked up by the Serbian Security Intelligence Agency and will be extradited to the U.N. war crimes tribunal in The Hague.

“On behalf of the Republic of Serbia, we announce that Ratko Mladic has been arrested,” Tadic said, according to the Associated Press. “We ended a difficult period of our history and removed the stain from the face of the members of our nation wherever they live.”

President Obama congratulated Serbia on the arrest and said he looks forward to the “expeditious transfer” of Mladic to The Hague.

“Today is an important day for the families of Mladic’s many victims, for Serbia, for Bosnia, for the United States, and for international justice,” Obama said in a statement issued from Deauville, France, where he is attending a Group of Eight summit. “While we will never be able to bring back those who were murdered, Mladic will now have to answer to his victims, and the world, in a court of law. ... Those who have committed crimes against humanity and genocide will not escape judgment.”

Serge Brammertz, prosecutor of the International Criminal Tribunal for the Former Yugoslavia (ICTY), welcomed the arrest and said Mladic would stand trial before the tribunal. In a statement, he said the arrest “can have a positive impact on reconciliation in the region,” while also serving the cause of justice for war crimes victims.

“These victims have endured unimaginable horrors — including the genocide in Srebrenica — and redress for their suffering is long overdue,” Brammertz said. He said the arrest “clearly signals that the commitment to international criminal justice is entrenched” and shows that “people responsible for grave violations of international humanitarian law can no longer count on impunity.”

The arrest was also hailed by other Western governments and human rights activists as a landmark in international justice. They said it would send an unmistakable message to other leaders — including Sudanese President Omar Hassan al-Bashir and Libya’s Moammar Gaddafi, two leaders charged with mass atrocities by the International Criminal Court — that they will ultimately be held accountable.

“The long arm of the law has just gotten a good deal longer,” said Richard Dicker, an expert on international justice at Human Rights Watch. “Coming more than 15 years after the first indictment, the message is that justice never forgets. It’s a clear signal to those leaders who so confidently bank on impunity that they need to be looking over their shoulder.”

Mladic’s arrest by Serbian authorities might mark a turning point in the effort of Serbia, once considered a pariah state by the West, to become integrated into Europe and ultimately to become a member of the European Union. European governments have long believed that the Serbian military establishment protected Mladic and prevented his arrest.

The development also provided a major boost to the Hague-based tribunal, which has indicted more than 150 Bosnians, Croatians and Serbians on war crimes charges, including the late Serbian president Slobodan Milosevic and Bosnian Serb leader Radovan Karadzic.

After the announcment, U.N. Secretary General Ban Ki-moon said Mladic’s arrest marks a “historic day for international justice.” He also called the arrest “an important step in our collective fight against impunity as well as for the work of the ICTY.”

Staff writers Scott Wilson in Deauville and William Branigin in Washington contributed to this report.