Jakarta, Aug. 15 (SANA)A powerful magnitude of 7.7earthquakehas struck off the coast of Indonesia’s Flores Island, prompting authorities to issue a tsunami warning.

In a press statement,Indonesia’s national disaster agency, said the quake struck early on Saturday with an epicenter about 68 kilometers north-northwest of the city of Ende, in East Nusa Tenggara province. USGS put the depth at 10km.

Three aftershocks followed within half an hour, measuring magnitudes 5.9, 5.6 and 6.1.

Indonesia’s Meteorology, Climatology and Geophysics Agency issued atsunamiwarning for affected coastlines, urging residents to stay away from beaches and riverbanks and move to higher ground.

Tsunami waves with a height of less than a meter were recorded in a number of coastal areas, while initial reports indicated material damage to some homes and facilities, without recording an immediate death toll.

Indonesia, a vast archipelago of more than 17,000 islands, is prone to earthquakes and volcanic activity because of its location on the “Ring of Fire,” an arc of volcanoes and fault lines in the Pacific Basin.