Medical team members help patients outside a hospital after an earthquake and a tsunami hit Palu, on Sulawesi island, Indonesia on September 29, 2018.

Time was running out on Wednesday for anyone trapped in the rubble of a devastating earthquake and tsunami in Indonesia, five days after disaster struck, while increasingly angry survivors waited for an aid operation to move into high gear.

The official death toll from the 7.5 magnitude quake that struck the west coast of the island of Sulawesi last Friday stood at 1,234, many killed by tsunami waves triggered by the quake.

But officials fear the toll could soar, as most of the confirmed dead have come from Palu, a small city 930 miles northeast of Jakarta, and losses in remote areas largely cut off since Friday have yet to be determined.

Underlining a growing sense of urgency, President Joko Widodo was due to make his second visit to the disaster zone on Wednesday. He made an initial visit less than two days after the quake struck.

At least seven cargo planes arrived at Palu airport early Wednesday morning carrying tonnes of aid, some bedecked in the red and white national colors and stamped with the presidential office seal declaring: "Assistance from the President of Republic of Indonesia".

Widodo, who will seek re-election next year, is likely to face criticism if conditions do not improve quickly. He called on Tuesday for reinforcements in the search for survivors, saying everyone had to be found.

Sutopo Purwo Nugroho, spokesman of the National Disaster Mitigation Agency, said late on Tuesday rescuers had reached all four of the badly affected districts, which together have a population of 1.4 million, but he declined to give an estimate of casualties.

"We hope the death toll does not rise," he said. "We're continuing rescue operations but right now the team is racing against time."

He gave few details of the conditions rescuers had found, saying they were similar to those in Palu.

The quake brought down hotels, shopping malls and countless houses in Palu, while tsunami waves as high as 20 feet scoured its beachfront shortly afterwards.

About 1,700 houses in one neighborhood were swallowed up by ground liquefaction, which happens when soil shaken by an earthquake behaves like a liquid, and hundreds of people are believed to have perished, the disaster agency said.

Adding to Sulawesi's woes, the Soputan volcano in the north of the island, about 600 km northeast of Palu, erupted early on Wednesday but there were no reports of any casualties or damage. Ash was not expected to disrupt flights.