Indonesia evacuated hundreds of tourists from popular resorts and sent rescuers fanning across the holiday island of Lombok Monday after a powerful quake killed at least 91 people and reduced thousands of buildings to rubble.

The shallow 6.9-magnitude quake sparked terror among tourists and locals alike, coming just a week after another deadly tremor surged through Lombok and killed 17 people.

Rescuers on Monday searched for survivors in the rubble of houses, mosques and schools that were destroyed in the latest disaster on Sunday evening.

“There are challenges: the roads were damaged, three bridges were also damaged, some locations are difficult to reach and we don't have enough personnel,” said a spokesman for the national disaster agency, Sutopo Purwo Nugroho.

An operation was also under way on Monday to evacuate some 1,200 tourists from the Gili Islands, three tiny, coral-fringed tropical islands a few kilometres off the northwest coast of Lombok that are particularly popular with backpackers and divers.

Margret Helgadottir, a holidaymaker from Iceland, described people screaming as the roof of her hotel on Gili Air collapsed when the quake struck.

“We just froze, thankfully we were outside,” she told AFP tearfully from a harbour in Lombok where she had been evacuated to. “Everything went black, it was terrible.”

Footage posted online by Nugroho showed hundreds crowded onto powder-white beaches desperately waiting for transport off the normally paradise Gilis.

“We cannot evacuate all of them all at once because we don't have enough capacity on the boats,” Muhammad Faozal, the head of West Nusa Tenggara's tourism agency, told AFP, adding two navy vessels were on their way. “It's understandable they want to leave the Gilis, they are panicking.”

Local disaster officials said 358 tourists had been evacuated so far.

At least one person, an Indonesian holidaymaker, was killed on the Gili islands while another tourist died on nearby Bali.

Night of aftershocks

But it was Lombok which bore the brunt of Sunday evening's quake.

The shallow tremor sent thousands of Lombok residents and tourists scrambling outdoors, where many spent the night as strong aftershocks including one of 5.3-magnitude rattled the island.

The quake knocked out power in many areas, and parts of Lombok remained without electricity on Monday.

Nugroho said up to 20,000 people may have been evacuated from their homes on Lombok and paramedics, food and medication were badly needed.

Hundreds of bloodied and bandaged victims were treated outside damaged hospitals in the main city of Mataram and other hard-hit areas.

Patients lay on beds under wards sent up in tents, surrounded by drip stands and monitors, as doctors in blue scrubs attended to them.

Anguished relatives were huddled around loved ones in front of the main clinic in Mataram, as medical staff struggled to cope with hundreds of patients. Many were yet to be seen despite spending the night out in the open.

“I feel restless sleeping in a tent, I can't be at peace,” Nurhayati told AFP outside one hospital where she had brought her sick 70-year-old mother.

“What we really need now are paramedics, we are short-staffed, we also need medications,” Supriadi, a spokesman for Mataram general hospital, told AFP.

The rubble-strewn streets of Mataram were empty save for a few survivors picking nervously through the ruins.

Most of the victims were in the mountainous north and east of the island, away from the main tourist spots and coastal districts in the south and west.

Collapsed mosques

Najmul Akhyar, the head of North Lombok district, estimated that 80 per cent of that region was damaged by the quake.

“We need heavy equipment because some mosques have collapsed and we suspect some worshippers are still trapped inside,” he told Metro TV.

As authorities scrambled to assess the extent of damage in Lombok, some tourists were trying to leave.

“We tried to go to the airport but there was no taxi, no transport, no plan for evacuation,” French tourist Jina told Metro TV.

“Later I stopped a car and I asked a local please take me and my family to the airport and he said 'Okay no problem'.”

Singapore's Home Affairs Minister K. Shanmugam, who was in Lombok for a security conference when the earthquake struck, described on Facebook how his hotel room on the 10th floor shook violently. “Walls cracked, it was quite impossible to stand up,” he said.

Bali's international airport suffered damage to its terminal but the runway was unaffected and operations had returned to normal. Disaster agency officials said. Lombok airport was also operating.

Indonesia, one of the most disaster-prone nations on earth, straddles the so-called Pacific “Ring of Fire”, where tectonic plates collide and many of the world's volcanic eruptions and earthquakes occur.

In 2014, a devastating 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.