All but essential travel to the Gili Islands off the north-west coast of Lombok has been banned after a devastating earthquake struck the Indonesian holiday island region.

The Foreign and Commonwealth Office upgraded its travel advice amid reports of British holidaymakers describing chaotic scenes as they tried to evacuate.

More than 2,000 tourists have been evacuated from Lombok and 2,700 from the Gili Islands, renowned destination for divers.

Up to 100 people have been killed at 20,000 left homeless in Sunday’s 6.9 magnitude quake.

The impact was far greater than an earthquake that struck a week earlier, killing 16 people.

The FCO warned: “There is a risk of aftershocks, which could cause further damage to buildings and pose risks to safety.

“In the event of serious injury, access to immediate medical assistance on the islands is extremely limited.

“The Indonesian authorities are working to assist people to leave the Gili Islands via boat to Lombok should they wish to do so.

“We are in contact with the Indonesian authorities who are mobilising a response in the Gili Islands and Lombok, including to help people leave the Gili Islands should they wish to do so. Lombok and Bali airports are open and operational.

“The National Disaster Mitigation Agency (BNPB) 24-hour hotline can be contacted on +62 85792240799.”

Tourist Phillipa Hodge was at the Katamaran Hotel just north of Lombok’s main city of Mataram when the quake hit. She told the BBC the lights went out and the scene “became chaotic”.

Thailand-based inbound operator Khiri Travel said that extra flights are being added to take tourists out of Lombok but a fast boat service between Lombok and Bali was suspended due to high sea swells.

All clients and staff are safe, the company added.

Khiri Travel Indonesia and partners raised almost $4,000 in the aftermath of the July 29 to help local residents.

“Our staff had just returned from northern Lombok a few hours before the Sunday earthquake. They had been handing out food, blankets, mats and water tanks and filters to villagers in rural areas,” a spokesman said.

“Donations to help Lombok residents recover from the earthquakes can be made via the Khiri Travel Indonesia Lombok office.”

He added: “Over the next few weeks, Khiri Travel will provide options to change travel programmes, or move guests scheduled to visit Gili Islands to alternative accommodations.

“Without any further incidents, Khiri Travel believes it will be possible to resume normal travel to Lombok in a few weeks’ time, especially the largely unaffected south and eastern areas of the island. We will keep monitoring the situation.”

Take That singer Gary Barlow, who was in Bali, said that he had experienced seven previous earthquakes but “none as felt more deep and raw” than Sunday’s. The Times reported.