Hagatna (Guam), Aug 15 (IANS): After a week of threats from North Korea aimed at Guam, the island's residents on Tuesday thought the worst had happened when two radio stations accidentally broadcast an emergency civil danger warning, the media reported.

The two stations, a music channel and a Christian network, alerted listeners at 12.25 a.m. (local time) of an unspecified danger near the US territory, reports the Guardian.

Civil danger broadcasts are rare and are used to warn civilians of an imminent threat, such as a military strike or terrorist attack.

The warning lasted only 15 minutes and officials later stressed that a real emergency message would describe the type of threat.

"The unauthorised test was not connected to any emergency, threat or warning," Guam's Homeland Security Office said in a statement, adding it had worked with the radio stations to "ensure human error will not occur again".

"Residents and visitors are reminded to remain calm," George Charfauros, Guam's homeland security adviser, said in a statement.

"There is no change in threat level, we continue business as usual.

"We continue communication with our federal and military partners and have not received official statement warranting any concern for imminent threat to Guam," he added.

Last week, North Korea detailed a specific plan to fire four missiles into the waters around the island which is home to 162,000 people and hosts two US military bases, the Guardian reported.

On Monday, US Defence Secretary James Mattis said any missile fired at Guam would be shot down, and warned that an attack "could escalate into war very quickly".