The alarm warned of an air attack, reports CNBC.
Earlier, North Korean authorities threatened to launch a nuclear strike on the island.
AT 12. 15 local time Christian and music radio stations gave the signal of an air attack on the air. The transmission of the siren lasted a quarter of an hour.
"An unauthorized alarm was not associated with any emergency, threat or warning," Guam's internal security department.
Also, the security department promised not to allow such incidents any more.
Recall, as reported by URA-Inform, the DPRK threatened a missile attack by the United States. North Korean military are considering the possibility of launching missile strikes in the area of ??Guam Island in the Western Pacific.