WELLINGTON?A 6.4-magnitude earthquake struck the Fiji region on Monday, the US Geological Survey said, but no tsunami warning was immediately issued.

The undersea quake hit 321 kilometers (200 miles) west of Suva at a depth of 555 kilometers at 2:07 am (1407 GMT), USGS said.

The Pacific Tsunami Warning Centre which monitors the region and issues bulletins in the event of a tsunami being generated had no such warning in force.

The area lies on the Pacific "ring of fire", a highly active tectonic zone that frequently experiences earthquakes and volcanic eruptions.