Indonesian security forces and emergency workers were racing on Monday to aid victims of a magnitude 7 earthquake on Lombok that killed at least 98 people, while tourists were being evacuated from the worst-hit areas.
The tremor, which came just a week after another quake killed 17 people on the island, was also felt on the neighbouring resort island of Bali, where frightened tourists ran onto the streets.
The earthquake struck just 10km underground, according to the US Geological Survey, and was followed by a series of strong aftershocks, prompting many to spend the night outside.
"The search and rescue team is still scouring the scene and evacuating (people)," national disaster agency spokesman Sutopo Purwo Nugroho said. "We estimate the number of victims will rise."
He described the damage as "massive" in the north of Lombok, citing an example of a collapsed mosque where worshippers are believed to have been buried during evening prayers. The rescue operation has been hampered by a lack of heavy equipment.
Some areas still hadn't been reached, with rescuers hampered by collapsed bridges, electricity blackouts and damaged roads blocked with debris.
He said the death toll had risen to 91 and more than 200 people were seriously injured. Thousands of homes and buildings were damaged. The death toll was revised to 98 later on Monday.
Almost 1,000 tourists were being evacuated from Indonesia's tiny Gili Islands, where the damage was extensive.
The Gilis are three coral-fringed tropical islands a few kilometres off the northwest coast of the larger Lombok island that are popular with backpackers and divers.
A British tourist on Gili Trawangan island said thousands of people, locals and tourists, were trying to get off Trawangan, after spending a night outdoors.
Saffron Amis from Brighton said thousands of people fled to a hill near the hostel where she was staying after Sunday evening's quake, fearing a tsunami.
She said: "There was a lot of screaming and crying particularly from the locals. We spoke to a lot of them and they were panicking about their family in Lombok."
There was widespread building damage and a somber mood on the island a day after the quake, Amis said, adding she felt lucky to be unharmed.
Mr Sutopo saod some 200 "domestic and foreign" tourists had already been taken off the islands. "There are 700 more tourists still waiting to be evacuated," he added.
Long lines were seen at the airport in Lombok's main town, Mataram, as foreign visitors scrambled to leave.
The Garuda Indonesia airline said it was adding extra flights, and AirAsia Group CEO Tony Fernandes tweeted that the budget carrier would also try to assist the evacuation efforts.
Tourists spoke of their terror as the earthquake struck. "I was at the rooftop of my hotel and the building started swaying very hard. It felt like two metres to the left, then two metres to the right, I could not stand up," Frenchman Gino Poggiali, 43, told Reuters.
Mr Poggiali's wife Maude, 44, said they had been holidaying with their two children and were also caught up in another powerful earthquake last week.
"This is it for me in Indonesia," she said. "Next time we will stay in France or somewhere close."
Australia's home affairs minister tweeted that he and his delegation had been safely evacuated in darkness from a Lombok hotel where they had been staying during a regional security conference.
Home Affairs Minister Peter Dutton told Fairfax Media that he was on the hotel's 12th floor when the quake struck. He said the quake "was powerful enough to put us on the floor" and cut power.
Singapore Law and Home Affairs Minister K. Shanmugam, who was on the 10th floor of a hotel in the Lombok town of Mataram at the time of the quake, wrote on Facebook that his room shook violently and walls cracked.
"It was quite impossible to stand up. Heard screams. Came out, and made my way down a staircase, while building was still shaking. Power went out for a while. Lots of cracks, fallen doors," he wrote.
A tsunami warning was issued but later lifted. Lombok is a popular tourist destination, drawing in visitors with surfing, beaches and hiking trails.
The earthquake of last week triggered landslides that briefly trapped trekkers on popular mountain hiking routes.
Najmul Akhyar, district chief of North Lombok, told local media that he was unable to assess the entire situation due to an electrical blackout.
Television host and celebrity tweeter Chrissy Teigen was on the nearby island of Bali with her husband John Legend, the singer, and their two young children as the earthquake struck.
Ms Teigen tweeted: "Bali. Trembling. So long."
She added: "Oh man. We are on stilts. It felt like a ride."
Dwikorita Karnawati, head of the agency for meteorology, climatology and geophysics, advised people not to panic. "Please go to a place with higher ground, while remaining calm."
Ms Karnawati added that small waves just 15cm (6 inches) high had been reported in three villages. A nearby volcano was evacuated after the earthquake struck.
Indonesia straddles the so-called Pacific "Ring of Fire", where tectonic plates collide, making the nation one of the most disaster prone in the world.
Some 90 per cent of the world's earthquakes happen in this region. Other countries including Bolivia, Chile, Japan, and the US west coast also sit on the "Ring of Fire."
In 2004 a tsunami triggered by a magnitude 9.3 undersea earthquake off the coast of Sumatra in western Indonesia killed 220,000 people in countries around the Indian Ocean, including 168,000 in Indonesia.
Why are we so bad at predicting earthquakes?
Residents in Mataram felt a strong jolt, causing them to flee their buildings. "Everyone immediately ran out of their homes, everyone is panicking," Iman, a local resident, told AFP.
Rita Siswati, another local, told AFP the tremor had caused a power outage, and said patients were being evacuated from the main hospital.
The Indonesian Red Cross said in a Tweet that it helped a woman give birth after the quake and that she named the boy 'Gempa', which means earthquake.