BELGRADE, SERBIA - Former Bosnian Serb leader Radovan Karadzic, accused architect of massacres that made him one of the world's top war-crimes fugitives, was arrested Monday evening in a raid that ended a 13-year manhunt.

Karadzic is the suspected mastermind of mass killings that the U.N. war crimes tribunal described as "scenes from hell, written on the darkest pages of human history." They include the 1995 massacre of 8,000 Muslims in Srebrenica, Europe's worst slaughter since World War II.

"This is a very important day for the victims who have waited for this arrest for over a decade. It is also an important day for international justice because it clearly demonstrates that nobody is beyond the reach of the law," said Serge Brammertz, the tribunal's head prosecutor.

Serbian President Boris Tadic's office said Karadzic was taken before the investigative judge of Serbia's war crimes court -- a legal procedure that indicates he could soon be extradited to the U.N. court at The Hague, Netherlands.

Karadzic would be the 44th Serb suspect extradited to the tribunal. The others include former President Slobodan Milosevic, who was ousted in 2000 and died in 2006 while on trial on war crimes charges.

Heavily armed special forces were deployed around the war crimes court in Belgrade where Karadzic was reportedly being held.

In Washington, the White House called the arrest "an important demonstration of the Serbian Government's determination to honor its commitment to cooperate with the International Criminal Tribunal."

300,000 deaths

The former Bosnian Serb leader has topped the tribunal's most-wanted list since his indictment in July 1995, and Serbia has been under increasing international pressure to find and turn him over.

"He was at large because the Yugoslav army was protecting him. But this guy in my view was worse than Milosevic," Richard Holbrooke, former U.S. ambassador who negotiated an end to the Bosnian War, told CNN. "He was the intellectual leader."

Holbrooke calculated the Karadzic is responsible, directly or indirectly, for the deaths of 300,000 people, because without him there would have been no war or genocide.

The charges against him, last amended in May 2000, are genocide, extermination, murder, willful killing, deportation, inhumane acts, and other crimes committed against Bosnian Muslim, Bosnian Croat and other non-Serb civilians in Bosnia and Herzegovina during the 1992-1995 war. The specific allegations include six counts of genocide and complicity in genocide and two counts of crimes against humanity, as well as violating laws of war and gravely breaching the Geneva Conventions.

The indictment alleges that Karadzic, in concert with others, committed the crimes to secure control of areas of Bosnia which had been proclaimed part of the "Serbian Republic" by significantly reducing its non-Serb population.

"These offenses include a brutal campaign of ethnic cleansing directed at non-Serbs, organized attacks on places of worship, the operation of concentration camps and the mass murder of thousands of Bos- nian Muslim and Bosnian Croat civilians," the White House said in a statement.

The fugitive's wife, Ljiljana, told The Associated Press by phone from her home in Karadzic's former stronghold, Pale, near Sarajevo that her daughter Sonja had called her before midnight.

"As the phone rang, I knew something was wrong. I'm shocked. Confused. At least now, we know he is alive," Ljiljana Karadzic said.

What's next

It will be months at least before Karadzic stands trial at the U.N. tribunal.

The complexity of a case encompassing most of the worst atrocities of the 1992-95 Bosnian war, along with legal wrangling and a packed docket, are expected to delay the start of the trial at the Netherlands-based court.

Authorities in Serbia, who arrested the former Bosnian Serb leader Monday, must first confirm his identity and read him his lengthy indictment.

Under new legislation regulating Serbia's cooperation with the tribunal, Karadzic may then have to enter a plea in a Belgrade court. After that, Serbia can apply to extradite him to the Netherlands, a move Karadzic can appeal.

Court spokeswoman Nerma Jelacic said she did not know how long the legal process in Belgrade would take.

"I hope his transfer is going to be as soon as possible," she said.