Orban, who is seeking his third term, said he hoped for a heavy turnout to give legitimacy and a clear mandate for the future.
"Hungary has never experienced any tragedy like that and we are all astonished," Orban said. "Huge damage has occurred, we've lost lives, and the region's future livelihood has been lost. Someone must be to blame for this. The responsibility and the punishment ... must be commensurate with the damage caused and the costs of those damages."