One of three key routes leading to the summit of Mount Rinjani on Indonesia's Lombok Island has been cleared following an earthquake that stranded hundreds of trekkers on the volcano's slopes, the national park authority said on Monday.

"The Senaru trekking route on Mount Rijani is now clear," Mount Rijani National Park said in a Tweet.

"A helicopter is being used to drop logistics to tourists still in the ... area," it added in another Tweet.

Sutopo Purwo Nugroho, the disaster mitigation agency's spokesman, had said late on Sunday that out of 820 people on the slopes of the volcano when the earthquake struck earlier that day, 246 had been successfully evacuated.

He said 617 of those trekking at the time were foreigners.

Two trails were impassable following the earthquake, he said.

News portal Detik said two helicopters had been deployed to take the trekkers off the mountain and distribute food.

Agung Pramuja, an official of the West Nusa Tenggara Disaster Mitigation Agency, said the death toll from Sunday's earthquake stood at 16.

"The latest information from the team in the field is that today all the families stuck on Mount Rinjani will be evacuated via the Sembalun trail," said Asdiyanto, an official at the North Lombok Disaster Mitigation Agency.

"This is being handled by the management team from Mount Rinjani National Park," said Asdiyanto who, like many Indonesians, uses one name.

A magnitude 6.4 earthquake is considered strong and is capable of causing severe damage.

The Lombok quake struck at 6:47 a.m. (2247 GMT on Saturday) and was only 7 km, a shallow depth that would have amplified its effect.

It was centred 50 km northeast of the city of Mataram, according to the US Geological Survey, but it was also felt strongly to the west on the neighbouring island of Bali, Indonesia’s top tourist destination.

Earthquakes are common in Indonesia, which is located on the seismically active “Ring of Fire” on the rim of the Pacific Ocean.