Squads of orange-clad rescue workers clambered over the tangled remains of an Indonesian hotel Sunday, hoping to dig out 50 to 60 guests still feared trapped by an earthquake-tsunami disaster.

Authorities believe the 80-room Hotel Roa-Roa in the city of Palu on Sulawesi island was near capacity when the district was ravaged by a 7.5 magnitude quake and a tsunami wave Friday.

"It is assumed there are still 50 to 60 people trapped under the rubble," said disaster agency spokesman Sutopo Purwo Nugroho.

A South Korean citizen is among those believed to be stuck inside.

Rescue workers are making the hotel a focus of their efforts to save lives.

But they now face a race against time to locate and extract survivors before injuries, exhaustion or dehydration take hold.

"We even heard people calling for help there at the Roa-Roa hotel yesterday," Muhammad Syaugi, head of the national Search and Rescue Agency, told AFP.

At least one person has been pulled out alive, he added.

Video posted by the agency on Sunday showed weary rescuers carrying one body wrapped in black plastic out on a stretcher.

Until Friday, the Roa-Roa was a modern chic hotel catering to business travellers, with views of the Makassar Strait and cloud-shrouded mountains in the distance.

It offered guests "easy access to the shopping malls, Talise Beach, market, restaurants" for around US$30 a night.

Now its Ray Eames-style designer armchairs and whitewashed surfaces are buried beneath a mangled heap of rebar, dust and concrete.