"This is being handled by the management team from Mount Rinjani National Park", said Asdiyanto who, like many Indonesians, uses one name.
"It happened all of a sudden around 6 in the morning", said this survivor.
The Red Cross is still trying to ascertain how many people could be missing, IFRC spokeswoman Husni told CNN.
The United States Geological Survey said the natural disaster struck at 6:47 am local time (22:47 UTC Saturday) at a depth of seven kilometers (four miles). Bali and Lombok airports are still operating, the spokesperson said.
"There was about 20 seconds of shaking, the water in the pool was making quite large waves", said Jean Paul Volchaert, who owns the Puncak Hotel.
"I've been walking around but so far there is no damage".
The US Geological Survey said the quake was shallow, striking at a depth of just seven kilometres which amplified the shake.
In February, an quake of that strength hit Taiwan, killing 17 people and injuring hundreds more.
It is frequently hit by quakes, majority harmless.
The jolt was felt some 100 km away in the bustling holiday island of Bali, although there were no immediate reports of damage there.
Hiking at Mount Rinjani had been suspended due to landslides but the Bali airport was operating normally, the U.S. Embassy in Jakarta tweeted. The two of the aftershocks after the main quake had an intensity of more than 5.0 on the Richter Scale.
Indonesia's geophysics and meteorology agency said at least 11 aftershocks were recorded after the quake.
Indonesia's geophysics and meteorology agency said at least 11 aftershocks were recorded after the 6.4-magnitude quake.
Authorities issued a yellow alert, which suggested that some casualties are a possibility. The disaster has left at least three dead and inflicted damage to houses on the island.
Five children were among those killed by the 6.4-magnitude tremor, which sent people running in panic and triggered landslides.
Quakes are common in Indonesia, which is located on the seismically active "Ring of Fire" that surrounds the shores of the Pacific Ocean.