The disaster that devastated Indonesian island of Sulawesi has left at least 844 people dead. Volunteers have begun burying victims in a mass grave.

President Joko Widodo has opened the door to dozens of international aid groups and NGOs to help reach remote areas that still have not been received help since the twin disasters.

Rescue workers have already begun to complain of medicine shortages and a lack of the necessary equipment to reach survivors trapped in collapsed buildings.

As a result, authorities in the city of Palu fear the death toll will skyrocket in the coming days, among other things amid disease outbreaks caused by decomposing bodies.

The UN has estimated that some 191,000 people in the region are in need of urgent help.

In the hills above Palu, volunteers filling a mass grave were instructed to prepare for a total of 1,300 victims to arrive.

Trucks arrived with bodies wrapped in orange, yellow and black body bags. They were dragged into the grave and motorized diggers poured earth on top.

Meanwhile, nearly 50,000 people remain displaced and various parts of the nation paralysed amid the recovery efforts.