An earthquake measuring 6.3, epicentred about 600km south of Tonga this afternoon, was not felt in Tongatapu.

The earthquake reported by the USGS at 1:07pm Tonga time, was located at 26.353 S, 177.776 W or about 320 km north of Raoul Island in the Kermadecs, at a depth of 35km.

It was the second of two large quakes in the area, an earlier 6.0 earthquake having been reported by the USGS at 10:39 pm on July 17 Tonga time.

At Tonga's meteorogical office, 'Ofa Taumoefolau, a forecaster, said that no tsunami warning had been received, following the quakes. "They were too deep to make a tsunami," he said. "But a larger earthquake of over 6.5 could make a tsunami." No warning has been issued for today.

Residents in the Tongan capital Nuku'alofa or in Tongatapu were not aware of today's quake, but people have not forgotten the violent shaking from last year's May 4 magnitude 8 earthquake in Tonga.