A powerful 7.7-magnitude earthquake struck off the coast of Indonesia's Flores Island early Saturday, killing at least 38 people as rescue teams dig through collapsed buildings across the region's hardest-hit areas.

The country's disaster mitigation agency, BNPB, said the toll continues to rise as search operations expand.

The earthquake struck shortly before 05:00 local time at a depth of around 10 to 15 kilometres, according to Indonesia's meteorology and geophysics agency, with an epicentre roughly 68 kilometres northwest of Ende in East Nusa Tenggara province.

Shallow quakes result in damage on the surface, and in this case, it was followed by a number of aftershocks, which included one with magnitude 6.1.

According to Fathur Rahman, the leader of Maumere Search and Rescue Agency, there have been three regencies from where bodies were retrieved: Sikka, West Manggarai, and East Manggarai. Eight people have been found dead in one landslide incident in Reok.

An alert of a possible tsunami was issued right after the quake and caused evacuation of about 2,000 people by their own will, BNPB stated.

The alert was lifted about three hours later when Indonesia's Meteorology, Climatology and Geophysics Agency detected no major changes in the sea level.

Videos recorded from the port of Maumere show concrete fragments falling from a terminal building directly onto the passengers of the ferry. Some of them were pushed into the water because of the collapse of a gangway.

According to Arnold Welianto, one of the locals, he awoke to "very strong shaking". After checking on his kid, he joined his neighbours in escaping to higher ground.

BNPB Head Suharyanto said there were two people who had sustained serious injuries and 11 people who had suffered minor injuries as of Saturday afternoon.

Reports have indicated that there could be 54 houses damaged severely, five health facilities, three worship centres, six governmental buildings, one educational facility, and one warehouse, though it should be mentioned that the difficult terrain makes it hard to evaluate the extent of damage. Manggarai province has become one of the most affected areas.

The same stretch of coastline was struck by a similarly powerful quake in December 1992, when the resulting tsunami killed more than 2,500 people on Flores.