Thousands of children are living in makeshift shelters six months after a devastating earthquake and tsunami pounded the Indonesian city of Palu, aid agencies said Tuesday, as authorities wrestle with a "painfully slow" recovery.

The magnitude 7.5 quake and subsequent deluge razed swathes of the coastal town on Sulawesi island last September, killing more than 4,300 people, according to Indonesia's national disaster agency.

At least 170,000 residents from Palu and surrounding districts are still displaced and entire neighbourhoods are still in ruins, despite life returning to normal in other areas of the city.

"Six months after this disaster we are extremely concerned about the estimated 6,000 children still living in temporary accommodation such as tents, as well as the thousands more that are living in homes that have been damaged," said Tom Howells of Save the Children.

Salsa, 10, and her parents have lived in a tent with a dirt floor ever since the towering waves tore through their home in Donggala near the epicentre of the quake.

"The light here is from a battery lamp," the fifth grader said.

"Often when we sleep there are a lot of mice."

Monsoon rains have fanned outbreaks of malaria and dengue fever, while residents in hard-hit areas have been forced to navigate open sewers and mounds of sharp rubble.

The force of September's quake saw entire neighbourhoods levelled by liquefaction -- a process where the ground starts behaving like a liquid and swallows up the earth like quicksand.

Indonesia has said the damage bill in Palu topped $900 million. The World Bank has offered the country up to $1 billion in loans to get the city back on its feet.

The vast Southeast Asian archipelago is one of the most disaster-prone nations on Earth due to its position straddling the so-called Pacific Ring of Fire, where tectonic plates collide.