"The arrest of Ratko Mladic is a very positive development for the European Union, for Serbia's neighbours, but most of all for the rule of law in Serbia itself. The families of his countless victims deserve justice," European Commission President Jose Manuel Barroso said in a statement.

Enlargement Commissioner Stefan Fuele called a special press conference on Mladic's arrest on Thursday.

"Justice is being served, and a great obstacle on the Serbian road to the European Union has been removed," Fuele said, adding that "this is a big day for Serbia, but also for the Western Balkans and for all of us."

Fuele paid a special tribute to Serbian President Boris Tadic for "his leadership and personal role in not only bringing General Mladic to the Hague tribunal, but also in playing an important role for reconciliation and regional stability in the Western Balkans."

When asked by a reporter whether it was reasonable now to exert pressure on Serbia to hand over the sole remaining fugitive, Croatian Serb rebel leader Goran Hadzic, Fuele said it was now up to the Hague tribunal's chief prosecutor, Serge Brammertz, to assess Serbia's cooperation. He added that the Serbian authorities had pledged to arrest the remaining fugitives, that they arrested Mladic today and that he had no reason to doubt that they would not do the same in the case of Hadzic.

"It's of course a very important day for international justice and for the rule of law. Mr Mladic will now face the charges against him in the International Tribunal; charges which are of course of a very serious nature. And we think back to events in Sarajevo and perhaps especially in Srebrenica. So today more than ever I think about the families and friends of the victims of the conflict and I feel it is really important that we remember them and think of them especially," said EU foreign affairs chief Catherine Ashton, who was visiting Belgrade.

"I know that people will also be thinking about Serbia and its future in the European Union. What I know is that we will approach that with renewed energy because of today," Ashton said, praising Serbian President Boris Tadic and the Serbian authorities for the arrest.

The arrest of Mladic was also hailed by European Parliament President Jerzy Buzek.