In an interview published in Sarajevo's Dnevni Avaz daily on Thursday, Ljajic said that the Serbian government and security services had fully reconstructed Mladic's movements from 1997 to 2003 and established beyond doubt that Mladic had been in Serbia all the time.
From 2003 onwards Mladic was mostly in Serbia, Ljajic said, adding that the last flat Mladic had been using for three years was abandoned in December last year.
Ljajic could not be more specific about Mladic's present whereabouts, saying only that there were some indications that were being checked.
He warned there there still existed a network supporting Mladic and that most of its members were from the Bosnian Serb entity.
"We know exactly how many people there are around Mladic... we know that the circle protecting him is very small," the official said.
The second most wanted fugitive from the UN tribunal, Radovan Karadzic, was never hiding in Serbia, Ljajic said.