Fazlic said underground concrete fortresses were built by the former Yugoslav military in the cities of Baghdad, Mosul, Kirkuk, Basra and Nassiriya after Iraqi officials toured similar facilities in former Yugoslavia.

"We also built the so-called "zero," "P" and "C" types of bunkers which were smaller and meant for the military, communications centers and so on but can also resist heavy bombardment and longer isolation," he said.

Fazlic said he took part in the building of more than a dozen underground bunkers in former Yugoslavia which was then led by late President Josip Broz Tito, who had warm relations with Saddam Hussein.

"We built all of these facilities in Iraq because they liked what they saw here," Fazlic said, citing a large bunker dug into a mountain near the southern Bosnian town of Konjic that was meant for the former Yugoslav government in case of war.