The drill, codenamed "ALARM-2026", is a routine check of the alert system and its procedures.
The alarm signal takes the form of a modulated sound lasting three minutes, while the all-clear is a continuous three-minute tone.
Sirens may be heard several times over the course of the test.
The RCB said alerts would mark the start and end of the exercise, and urged people not to evacuate or take any other action.
Poland's public alert system uses sound signals, verbal announcements and a yellow triangle symbol – displayed in public places, on emergency vehicles or in the media – to warn of and later stand down an alarm.
(ał)
Source: PAP, IAR