The woman identified by relatives and media reports as Juliana Marins, 26, went missing on Saturday at Mount Rinjani on Lombok island, which neighbours Bali.

Authorities think Marins fell and believe they sighted her on Monday but rescuers were held back because of bad weather.

"Yesterday morning we detected the victim. We deployed a team to the location but we were hampered by the very steep terrain and the foggy weather," Muhammad Hariyadi, head of Lombok's Mataram Search and Rescue Office, told AFP on Tuesday.

"When we detected her using a drone, she was not moving."

Rescuers said they were using thermal drones, mountaineering gear and a helicopter in a bid to reach the Brazilian, who was backpacking around Southeast Asia.

"One group is monitoring the evacuation using a thermal drone. The second team is doing the manual evacuation process with a rope as the main tool," said Hariyadi.

"This morning around 50 rescuers have been dispatched and we plan to send a helicopter team to scour the location."

An Instagram account set up by family and friends to call for her urgent rescue has amassed more than one million followers.

"Hang in there Juliana! Help is on the way!" read a post on the account.

The Brazilian embassy in Jakarta did not immediately respond to an AFP request for comment.

Marins' last posts on Instagram show her backpacking around Thailand and Vietnam before reaching Indonesia.

Lombok island is a tourist destination known for its idyllic beaches and lush greenery, and many try to climb Rinjani, Indonesia's second-tallest volcano, for its panoramic views.

In 2018 hundreds of hikers and guides became stranded by landslides on the mountain after a 6.4-magnitude earthquake struck the island. At least 17 were killed across the island including one on the mountain.