Nuclear attack siren warning

Hawaii dusts off nuclear attack warning siren

The resumption of the monthly tests comes amid a growing threat from North Korea's missile and nuclear programme.

Pyongyang has tested a series of ballistic missiles and in September carried out its sixth nuclear test.

Hawaii, in the Pacific, already has a monthly test of sirens warning of natural disasters, including tsunamis.

The nuclear attack signal uses a different, wavering tone, warning residents and tourists to stay indoors and await further instructions.