A strong 6.5-magnitude earthquake struck off the Pacific nation of Tonga on Saturday, the US Geological Survey said, but there was no immediate tsunami warning or reports of significant damage. The quake hit at 6:02 pm (06:02 GMT), 71 kilometers (44 miles) from the Tongan capital Nuku'alofa at a shallow depth of 10 kilometers, the USGS said, AFP reported.