Thailand was on Wednesday grasping the magnitude of the tsunami disaster amid criticism that meteorological officials had been too hesitant to warn of the risks of a sea surge in case they were wrong.

Thailand's meteorological department knew by 8.10am (local time) on Sunday about an hour before the first waves hit that a powerful earthquake had struck near Sumatra, and they discussed the possibility that the quake could cause large sea disturbances. The department had already distributed information pamphlets several years ago explaining the risks of tsunamis around southern Thai beach resorts.