The defence reported that the crash happened "during routine duties" as the self-propelled mobile anti-aircraft system travelled in a convoy with a military police escort.

"According to early reports, there are injured and dead in the accident," the ministry said without providing further details.

Later, the director of Kraljevo General Hospital Zoran Mrvic told state media that five people had died, including three children, and that another person was in serious condition.

The defence ministry announced that an investigation was underway into the accident, while police did not immediately give comment.