Civil defense sirens are expected to go off all over Greece on Wednesday as part of the annual military and public warning exercise dubbed Parmenion after the Macedonian general of Philip II and Alexander the Great.

Authorities have told citizens not to be concerned when they hear the first blast of the country's air-raid sirens, which are scheduled to go off at 11 a.m., blasting at 60-second intervals, and end at 11.05 a.m.

The exercise, Greece's biggest in military readiness, will run through October 4 with various coordination and preparedness exercises.