U.N. Secretary-General Ban Ki-moon, who was staying in Paris, hailed the capture of Mladic, who was on the run for 16 years, as "an historic day for international justice."
European Union foreign policy chief Catherine Ashton said in a statement that the international community expected "Ratko Mladic to be transferred to the International Criminal Tribunal for the former Yugoslavia without delay".
"Full cooperation with the ICTY remains essential on Serbia's path towards EU membership," she added. The ICTY tribunal in The Hague has charged him with genocide and other war crimes.
EU Enlargement Commissioner Stefan Fuele described today's events as the proof that Serbia had understood the key importance of reconciliation in the region.
Mevlut Cavusoglu, who is at the helm of the Parliamentary Assembly of the Council of Europe, said that the news about the apprehension of Mladic was great news for the future of Serbia, for the law and justice and struggle against impunity.
British Foreign Secretary William Hague congratulated Serbia on the arrest and called it a historic moment for the region burdened by the horrendous wars of the 1990s.
Our thoughts are today with the families of those killed in the besieged Sarajevo and with the families of the victims of genocide in Srebrenica, Hague said.
Commenting on the news, Slovenia's Prime Minister Borut Pahor said that "justice is slow but it prevails".
Swedish Foreign Minister Carl Bildt joined in congratulating Serbia on arresting Mladic.
Dutch Prime Minister Mark Rutte said that Mladic's apprehension was an important condition for Serbia's entry to the EU, but did not mean automatic accession.
"You need to look at the entire facts around every accession. This was an important element, but it does not mean that digital one-on-one the arrest of this man means accession. It does not work like that," Rutte told Dutch television, according to Reuters news agency.
Italian Foreign Minister Franco Frattini said that these developments showed Serbia's great democratic maturity and that this was a turning point which the EU welcomed.