The quake hit Lombok island early in the morning when many people were still sleeping. Around 40 people were injured and many fled into open fields away from collapsed buildings.
"We jumped out of our beds to avoid anything falling on our heads," said Jean-Paul Volckaert who was woken by the quake while sleeping in the Puncak Hotel near Senggigi on Lombok.
"I’ve been walking around but so far there is no damage. We were very surprised as the water in the pools was swaying like a wild sea. There were waves in the pools but only for 20 to 30 seconds," he told Reuters via telephone.
"The people in the villages may have damages. It’s still early morning here.”
The quake was centered 50 km (31 miles) northeast of the city of Mataram on the northern part of Lombok island, the U.S. Geological Survey (USGS) said.
A Malaysian tourist visiting the popular trekking destination of Mount Rinjani on Lombok was among those killed, according to East Lombok police M. Eka Fathurrahman.
Sutopo Purwo Nugroho, the disaster mitigation agency spokesman, posted on Twitter pictures of houses with collapsed roofs and walls.
"People are gathering on the streets and empty fields to avoid collapsing buildings," he said.
"The main focus now is evacuation and rescue. Some of the injured are still being treated at clinics."
Around 66 quakes were recorded after the initial 6.4 magnitude tremor, with the largest aftershock recorded at 5.7 magnitude, said the disaster mitigation agency.
The major quake was felt on the neighboring island of Bali, Indonesia's top tourist destination.
The quake forced authorities to close the Mount Rinjani national park. "Rinjani mountain climbing is closed temporarily because there are indication of landslide around the mountain," Nugroho, said in a statement.
The earthquake struck at 6:47 a.m. on Sunday (2247 GMT on Saturday) and was only 4.35 miles deep (7 km), a shallow depth that would have amplified its effect.
A magnitude 6.4 earthquake is considered strong and is capable of causing severe damage.
The European-Mediterranean Seismological Centre (EMSC), the European quake agency, put the magnitude at 6.5.
The earthquake was on land and did not trigger any waves or tsunami. Lombok is the next island east of Bali.
Quakes are common in Indonesia, which is located on the seismically active "Ring of Fire" that surrounds the shores of the Pacific Ocean.
(Reporting by Latief Apriaman in SEMBALUN, Fransiska Nangoy and Agustinus Da Costa in JAKARTA, Alison Bevege in SYDNEY; Editing by Michael Perry)