A man known as Milorad Komadic, who is believed to be Mladic, was arrested and authorities are currently carrying out tests to confirm his identity, the radio station reported.
Serbian President Boris Tadic has called a press conference for Thursday afternoon.
The information could not be independently verified by AFP for the moment. A high official of the Serbian intelligence service BIA contacted by AFP would not confirm the news.
“I don’t have any information about this. Go see what Tadic says,” Jovan Stojic said.
Mladic is the most wanted fugitive of the International Criminal Tribunal for the former Yugoslavia (ICTY).
He has been on the run since 1995 and faces charges of genocide, crimes against humanity and war crimes for his role in the Srebrenica massacre of 8 000 Muslim men and boys and the bloody siege of Sarajevo during the 1992-95 war in Bosnia.
The arrest of Mladic has been a key stumbling block in Serbia’s efforts to push forward its application for membership of the the European Union.
In Brussels, the European Union executive said that it had “all reason to believe” that the man arrested by Serbian authorities could be Mladic.
The claims of the arrest came on the same day that details of a new report by the ICTY’s chief prosecutor emerged in which Serbian authorities were accused of not doing enough to capture Mladic.