5.7-magnitude earthquake hits off Vanuatu island nation

A 5.7-magnitude earthquake hit northwest of the Pacific island nation of Vanuatu on Monday, the US Geological Survey said, but there were no immediate reports of casualties or damage.

The quake, which struck at a depth of 20 kilometres (12.4 miles) and about 250 kilometres northwest of Vanuatu's Santo island, was first reported as a 6.0 magnitude before being downgraded by the USGS.

No tsunami warning was issued.

Vanuatu is part of the "Ring of Fire," a zone of tectonic activity around the Pacific frequently subject to earthquakes and volcanic eruptions.

Last year the island nation was rocked by a series of quakes, including some that prompted tsunami warnings.