A powerful 7.7-magnitude earthquake has struck off the coast of Indonesia’s Flores island, triggering an early tsunami warning. The earthquake struck early on Saturday, with the US Geological Survey (USGS) placing its epicentre about 68 km north-west of Ende, off the northern coast of Flores.

The European-Mediterranean Seismological Centre (EMSC) also recorded the earthquake at magnitude 7.7, although it put the depth at 35 km. USGS estimated the depth at about 10km.

Indonesia’s Meteorology, Climatology and Geophysics Agency (BMKG) issued an early tsunami warning for several regions, including East Nusa Tenggara, South Sulawesi, West Nusa Tenggara and Southeast Sulawesi.

The agency urged people to stay away from beaches and riverbanks and called on residents in affected coastal areas to move to higher ground, according to the Associated Press.

At least three strong aftershocks followed the main earthquake. The USGS recorded tremors measuring 5.9, 5.6 and 6.1.

The USGS said its initial assessment indicated that casualties and damage were possible. Its PAGER system estimated that about 500,000 people had been exposed to very strong or severe shaking.

Videos shared on social media appeared to show a building collapsing in the Indonesian port of Maumere. The footage has not been independently verified. There were no immediate official reports of casualties or the extent of damage.

Australia’s tsunami warning centre said there was currently no threat to the country’s mainland, islands or territories.

The centre said the undersea earthquake would have “no tsunami threat to the Australian mainland, islands or territories”.

Indonesia is one of the world’s most earthquake-prone countries because it lies on the Pacific “Ring of Fire”, an arc of intense seismic activity stretching from Japan through South-East Asia and across the Pacific.

The country has experienced a number of devastating earthquakes and tsunamis, including the 9.1-magnitude earthquake off Sumatra in 2004, which triggered a tsunami that killed more than 220,000 people around the Indian Ocean. More than half of those deaths occurred in Indonesia.

In 2018, a 6.9-magnitude earthquake struck Lombok, killing hundreds, while a 7.5-magnitude earthquake and tsunami later hit Sulawesi, also killing hundreds. In November 2022, a 6.5-magnitude earthquake in West Java’s Cianjur region killed hundreds more.