Some 10,000 people have been evacuated on the Indonesian island of Lombok after a powerful 6.9 magnitude quake on Sunday left more than 90 people dead.
Witnesses spoke of chaos and terror as buildings collapsed and power and communication lines were cut.
Boats have been sent to evacuate more than 1,000 tourists from the nearby Gili islands.
Aid agencies said the priority was to provide shelter for residents too scared to return to their homes.
The agencies said the impact was far bigger than another quake that hit Lombok last week, killing 16 people.
What’s the latest on Lombok?
Sutopo Purwo Nugroho, a spokesman for the Indonesian Disaster Management Agency, said that the northern area of Lombok had suffered massive damage.
Three C-130 Hercules aircraft and two helicopters have been deployed to deliver tents and medical aid, but the earthquake has brought down roads and bridges, making areas difficult to reach.
Electricity supply in the worst-affected areas has been cut off and telecommunication networks are not working.
The death toll stands at 91, all Indonesians, but Mr Sutopo said that number would “definitely increase”. At least another 200 people have been injured.
He pointed to the situation at a collapsed mosque in the village of Lading-Lading in north Lombok, where a lack of heavy lifting equipment had made it difficult to locate victims.
One official said 80% of north Lombok had suffered damage.
The main city of Mataram was also badly affected, with medical staff struggling to cope with the injured at the damaged hospitals.
What about the Gili islands?
Situated off the north-west of Lombok and popular with backpackers and divers, they were badly hit, with a number of hotels damaged.
Video and still images showed hundreds of tourists flocking to the beach to be evacuated.
There have been reports of deaths on the islands but these have not been confirmed.
Hundreds of tourists have been taken off by boat, but hundreds still remain.
“We cannot evacuate all of them all at once because we don’t have enough capacity on the boats,” Muhammad Faozal, of West Nusa Tenggara’s tourism agency, told AFP.
“It’s understandable they want to leave the Gilis, they are panicking.”
What have victims and witnesses been saying?
Helen Milne told the BBC that her daughter, Laura, from Oxfordshire in the UK, is on the island of Gili Trawangan.
She said: “They are stuck on the island and are reporting rioting, fighting, and people can’t get on boats. There’s no water, no food, the shops have been ransacked. It’s a rapidly deteriorating situation out there for them.”
Another Briton on Gili Trawangan, James Kelsall, told the Press Association the subsequent tsunami warning was the most terrifying part.
“All the locals were frantically running and screaming, putting on life jackets. We followed them up to higher ground, which was a steep, uneven climb to the top of a hill in darkness.”
What are the quake details?
It struck at 19:46 local time (11:46 GMT) on Sunday at a fairly shallow depth of 31km (19 miles).
There have been more than 130 aftershocks since the quake hit.
Lombok is a roughly 4,500 sq km (1,700 sq miles) island east of the slightly larger island of Bali. The two islands are home to about three and four million people respectively.
Both are popular with tourists who visit beaches and hiking trails.
Indonesia is prone to earthquakes because it lies on the Ring of Fire – the line of frequent quakes and volcanic eruptions that circles virtually the entire Pacific rim.
More than half of the world’s active volcanoes above sea level are part of the ring.