Authorities on the earthquake ravaged island of Lombok were allegedly demanding money from tourists before they would let them onto rescue boats.

After the 6.9-magnitude quake struck, killing more than 100 people, some survivors attempted to flee the Indonesian island.

Katy Flay, who was on holiday with her partner, told her brother authorities were demanding money before they would allow tourists onto rescue boats.

"We have tried to get on many boats. Boats [are] leaving half empty as you need a ticket... no boats for everyone, just selected people," the 333-year-old said in comments he later relayed to The Guardian. "People are punching and hitting each other."

American holidaymaker Michelle Thompson also described a scramble to get on boats leaving for the main island during which her husband was injured.

"People were just throwing their suitcases on board and I had to struggle to get my husband on, because he was bleeding," she said.

Valentin Valla, a French tourist in the town of Mataram, said the quake woke up tourists who ran out of their hotel, but there was no apparent damage.

Indonesia's National Disaster Mitigation Agency (BNPB) said it expected the death toll to rise once the rubble of more than 13,000 houses was cleared away after two powerful quakes in a week.

Power and communications were severed in some areas, with landslides and a collapsed bridge blocking access to areas around the epicentre in the north.

The military said it would send a ship with medical aid, supplies and logistics support.

Indonesia sits on the Pacific Ring of Fire and is regularly hit by earthquakes. In 2004, the Indian Ocean tsunami killed 226,000 people in 13 countries, including more than 120,000 in Indonesia.

Lombok earthquake: more than 500 climbers trapped on Indonesia volcano

Officials said more than 2,000 people had been evacuated from the three Gili islands off the northwest coast of Lombok, where fears of another tsunami spread.

BNPB spokesman Sutopo Purwo Nugroho said emergency units in its hospitals were overflowing and some patients were being treated in parking lots.

The main hospital in the town of Tanjung in the north was severely damaged, so staff set up about 30 beds in the shade of trees and in a tent on a field to tend to the injured.

A boy with a heavily bandaged leg wailed in pain, an elderly man wore a splint improvised from strips of cardboard on a broken arm, and some hurt by falling debris still had dried blood on their faces.

The Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) said more than 120 aftershocks were recorded after Sunday evening's quake.

Lombok had already been hit on July 29 by a 6.4 magnitude quake that killed 17 people and briefly stranded several hundred trekkers on the slopes of a volcano.

At magnitude 6.9, Sunday's quake released more than five times the energy of the earlier one, the US Geological Survey website said.

The tremor was powerful enough to be felt on the neighbouring island of Bali where, BNPB said, two people died.

Despite it being a popular tourist destination, no foreigners were recorded among the dead, Mr Nugroho told a news conference. Some 236 people were injured and more than 20,000 displaced, he said.

"We have yet to ask for help from the international (community). But if there's any friendly country who wants to offer help, please do," Mr Nugroho said.

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According to media reports, a 7.0 magnitude earthquake hit Indonesia's island of Lombok on 05 August killing at least 82 people. EPA/MADE NAGI MADE NAGI EPA Powerful earthquake rocks Indonesia's Lombok island Map locating the earthquake in Lombok Reuters Powerful earthquake rocks Indonesia's Lombok island Indonesian soldiers carry the body of an earthquake victim Reuters Powerful earthquake rocks Indonesia's Lombok island Evacuation from Gili Trawangan in Indonesia James Kelsall/PA Powerful earthquake rocks Indonesia's Lombok island Workers cleanup parts of a shopping mall building which collapsed after an earthquake, in Denpasar, Bali EPA Powerful earthquake rocks Indonesia's Lombok island Recovered items sit next to destroyed buildings in Pemenang in northern Lombok AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Hundreds of people attempting to leave Gili Trawangan AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Indonesian local residents stay outside of their collapsed houses EPA Powerful earthquake rocks Indonesia's Lombok island Rescue personnel stands next to a motorcycle that fell down at a mall in Bali's capital Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Hospital staff treat patients outside a hospital after a major earthquake rocked Indonesia's Lombok island, in Mataram AFP/Getty Powerful earthquake rocks Indonesia's Lombok island People affected by the earthquake rest at a temporary shelter in Lombok AP Powerful earthquake rocks Indonesia's Lombok island A man removes debris outside a mall in Bali's capital Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island People react following an earthquake in Ampenan district, Mataram, Lombok Reuters Powerful earthquake rocks Indonesia's Lombok island A hospital patient is moved outside of the hospital building in Denpasar, Bali EPA Powerful earthquake rocks Indonesia's Lombok island A policeman gestures as he walks next to damaged bikes and debris at a mall in Bali's capital Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island People next to an ambulance near the Golden Palace Hotel after an earthquake hit Lombok Reuters Powerful earthquake rocks Indonesia's Lombok island Residents stand next to bikes and debris at a mall in Bali's capital Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Indonesian soldiers tend to a woman injured in the earthquake at a makeshift hospital in Lombok AP Powerful earthquake rocks Indonesia's Lombok island Tourists wait outside a hotel in Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island People clean up debris following a strong earthquake on nearby Lombok island, in Denpasar Reuters Powerful earthquake rocks Indonesia's Lombok island An ambulance near Golden Palace Hotel after an earthquake hit Lombok Island Reuters Powerful earthquake rocks Indonesia's Lombok island Indonesians stand on road outside a mall in Bali's capital Denpasar AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Security and mall personnel walk over debris AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Residents wait as they evacuate to higher ground AP Powerful earthquake rocks Indonesia's Lombok island An ambulance rushes out of the hospital AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Hospital patients and relatives wait outside in Mataram AFP/Getty Powerful earthquake rocks Indonesia's Lombok island Hospital patients and relatives stand outside after being evacuated in Mataram AFP/Getty Powerful earthquake rocks Indonesia's Lombok island A hospital patient is moved outside EPA Powerful earthquake rocks Indonesia's Lombok island Residents evacuate by motorcycle Reuters Powerful earthquake rocks Indonesia's Lombok island A hospital patient is moved outside EPA

British-based charity Oxfam said it was providing clean drinking water and tarpaulin shelter sheets to 5,000 people and planned to intensify aid delivery.

The United Nations has offered to support rescue and relief efforts if required.

The Indonesian Red Cross said on Twitter it had helped a woman give birth at a makeshift health care station after the quake. One of the names she gave the baby boy was "Gempa", which means earthquake.

Among those displaced were residents of a northern village called Mentigi, who fled to nearby hills. Blue tarpaulins dotted the landscape as people prepared to spend the nights outdoors because of aftershocks or because their homes were destroyed.

"We are getting some aid from volunteers, but we don't have proper tents yet," said a 50-year-old villager sheltering with his wife and children, who gave his name only as Marhun.

Sengiggi, a seaside tourist strip on Lombok, looked abandoned. Amid collapsed homes, most hotels seemed to have shut and beaches were deserted. The few restaurants left open were rationing food.

Long lines formed at the airport of Lombok's main town, Mataram, as foreign visitors cut their holidays short. BNPB said 18 extra flights had been added for leaving tourists.

"I was at the rooftop of my hotel and the building started swaying very hard ... I could not stand up," said Gino Poggiali, a 43-year-old Frenchman, who was with his wife and two children at the airport.

His wife Maude, 44, said the family was on Bali for the first quake and Lombok for the second.

"This is it for me in Indonesia. Next time we will stay in France, or somewhere close," she said.