"There are elements that indicated it could have come from both."
Air crash investigators have pulled most of the drone's remaining parts from a large crater it created on impact, including a partly damaged black box that should reveal the drone's flight path.
Croatian officials have criticised Nato for what they called a slow reaction to a very serious incident and called into question the readiness of the military alliance's member states to respond to a possible attack.
Nato said the alliance's integrated air and missile defence had tracked the object's flight path. But Croatian officials said the country's authorities weren't informed and that Nato reacted only after questions were posed by journalists.
"If this situation had been detected and resolved in time in neighbouring countries, we would not be here today," Banozic said.
"We will seek answers to what happened. The defence ministers of Romania and Hungary said that day they were evaluating what happened. We are waiting for an answer."
Croatian investigators identified the unmanned aircraft that crashed in Zagreb as a Soviet-era Tu-141 that was used for reconnaissance missions in both countries in the 1980s. - AP
