SINGAPORE - A minute-long "important message" signal will be sounded through the island-wide Public Warning System sirens network at 12.05pm on Friday (Sept 15) by the Singapore Civil Defence Force (SCDF).

SCDF advised the public not to be alarmed, and to tune in immediately to any local radio station for a brief message after hearing the signal.

Those who miss the radio message can visit the SCDF website at www.scdf.gov.sg to find out more.

The "important message" signal will also sound on all smartphones that have the SGSecure mobile app installed, and if they are not on silent or vibration mode.

The signal will stop sounding after 20 seconds or once the message is acknowledged. A brief text message will be sent after that.

The signal sounding and radio broadcast exercise is held annually as part of SCDF's efforts to familiarise the public with the Public Warning System's signals and to raise awareness of how the public should react upon hearing the signal.