Indonesian Army medics treat an injured woman at a makeshift camp in Palu in Central Sulawesi on October 4, 2018, after an earthquake and tsunami hit the area on September 28.

International efforts to help survivors of Indonesia's devastating earthquake and tsunami gathered pace on Thursday as concern grew for hundreds of thousands with little food and water, six days after disaster struck.

Desperate residents on the west coast of Sulawesi island were scavenging for food in farms and orchards as the government struggled to overcome shortages of water, food, shelter and fuel in a disaster zone with no power and degraded communications.

Chaos has loomed at times with angry people in the region's main city of Palu, 1,500 km (930 miles) northeast of Jakarta, looting shops and thronging its small airport, scrambling for any flight out.

The official death toll from last Friday's 7.5 magnitude quake has risen to 1,407, many killed by tsunami waves and landslides it triggered. Officials say the toll will rise.

Most of the confirmed dead have come from Palu and losses in remote areas remain unknown. Communications are down and bridges and roads have been destroyed or blocked by slips.

But international efforts to help are gearing up, after the government overcame a traditional reluctance to take foreign aid.

"The government of Indonesia is experienced and well-equipped in managing natural disasters, but sometimes, as with all other countries, outside help is also needed," U.N. Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator Mark Lowcock said in a statement.

He announced an allocation of $15 million.

The International Federation of Red Cross and Red Crescent Societies said it was appealing for 22 million Swiss francs ($22 million) to help Indonesia.

The United States had provided initial funding, deployed government disaster experts and was working to determine what other help could be given, the State Department said earlier this week.

Some aid from Britain and Australia as also due to arrive on Thursday.

In all, about 20 countries have offered help, Indonesia has said.

In Palu, some shops and banks reopened on Thursday and a major mobile phone network was back into operation. A sense of calm seemed to be returning with orderly queues at petrol stations after the arrival of fuel shipments.