A powerful magnitude 7.7 earthquake struck off Indonesia's Flores region early Saturday, damaging homes and public buildings and sending frightened residents rushing to higher ground after authorities issued a tsunami warning.

The earthquake struck at 5:58 a.m. Indonesia time, according to the U.S. Geological Survey (USGS), at a depth of just 10 kilometres. Its epicentre was located about 68 km (42 miles) north-northwest of Ende, in East Nusa Tenggara province.

There were no immediate reports of casualties, but early accounts from the affected region indicated that the strong shaking damaged buildings and public facilities. Several aftershocks were also reported following the main earthquake.

Tsunami warning issued across four Indonesian provinces

Indonesia's Meteorology, Climatology and Geophysics Agency issued a tsunami warning covering parts of East Nusa Tenggara, West Nusa Tenggara, South Sulawesi and Southeast Sulawesi.

Residents in affected coastal areas were urged to stay away from beaches and riverbanks and move to higher ground. Officials were monitoring coastal tide gauges for possible changes following the shallow undersea earthquake near Flores Island.

The warning came as authorities assessed the extent of the damage caused by the powerful tremor.

'Many buildings here were damaged'

The earthquake was felt across much of Flores Island, where residents described scenes of panic as the ground shook.

Yohanna Embu, a resident of Sikka regency in East Nusa Tenggara, said several buildings had been damaged and people fled towards higher ground.

“Many buildings here were damaged ... I saw that the waiting room at the Pelni port terminal in Maumere had collapsed,” she said.

Officials had not yet released an estimate of the number of damaged buildings or any confirmed casualty figures.

Why Indonesia is highly vulnerable to earthquakes

Indonesia is one of the world's most earthquake- and volcano-prone countries. The vast archipelago, made up of more than 17,000 islands, lies along the Pacific “Ring of Fire”, an area marked by numerous active volcanoes and fault lines.

The latest earthquake also comes with a painful historical reminder for Flores.

In December 1992, a magnitude 7 earthquake triggered a tsunami that killed about 2,500 people on Flores, an island in eastern Indonesia.

With AP inputs