Maumere (Indonesia), Aug 16: A powerful 7.7-magnitude earthquake struck off Indonesia's Flores island early Saturday, killing at least 20 people, injuring six others and leaving two missing. According to Indonesian authorities, the shallow undersea quake struck at 5.58 am local time at a depth of 10 km, with its epicentre located about 68 km north-northwest of Ende in East Nusa Tenggara province. The United States Geological Survey (USGS) said the main tremor was followed by several aftershocks. The quake caused extensive damage across Flores island, with reports of collapsed homes, damaged public buildings and landslides. Authorities said at least two people were killed when buildings collapsed, while rescue teams continued to assess the full extent of the destruction. Indonesia's disaster management agency said six people were injured and two remained missing after a landslide triggered by the earthquake. Search and rescue operations were underway in the worst-hit areas. The earthquake also prompted authorities to issue a tsunami warning for parts of East Nusa Tenggara, West Nusa Tenggara, South Sulawesi and Southeast Sulawesi provinces. Residents living along the coast were advised to move to higher ground and avoid beaches and riverbanks. However, the warning was later lifted after monitoring showed no significant sea-level changes. Television footage showed patients being evacuated from hospitals as a precaution. Medical staff moved beds, oxygen cylinders and other equipment outdoors while temporary treatment areas were established to handle emergency conditions. Residents described scenes of panic as the tremors shook large parts of Flores island. "Many buildings here were damaged. I saw that the waiting room at the port terminal in Maumere had collapsed," said Yohanna Embu, a resident of Sikka regency. At St Peter Major Seminary in Sikka, students attending morning Mass fled after part of an assembly hall roof collapsed. "Our students and nuns ran out in panic beneath a collapsing roof," said Rev Guidelbertus Tanga, rector of the seminary. "At least one priest suffered a broken leg after jumping from the second floor of a building during the quake." Indonesia, an archipelago of more than 270 million people, sits on the Pacific Ring of Fire, making it one of the world's most earthquake-prone regions. The country frequently experiences seismic activity due to its location on a series of active tectonic fault lines. Inputs from AP & PTI