Helicopters are spraying disinfectant on neighbourhoods in Palu, a city in Indonesia that was devastated by September's earthquake and tsunami, in a bid to combat disease risks from the thousands of bodies which are thought to still be buried in the worst hit areas.

The country's disaster agency spokesperson, Sutopo Purwo Nugroho, said it was necessary because of the large number of victims not recovered by the rescue operation that ended on 12 October.

"Bombing and spraying of disinfectants is an effort to anticipate the spread of diseases through vectors such as flies, cockroaches, or mice," he said, adding that three neighbourhoods would be covered.

Some ground spraying was also carried out but much of the land was too unstable for that to be done comprehensively, he added.

Ahmad Yurianto, head of the Ministry of Health's crisis centre, said that groundwater needed to be checked regularly for contamination.

He added that drainage needed to be established to collect rainwater before it entered the city's river.

Rescuers burn debris (Associated Press)

The 7.4-magnitude earthquake, which hit Indonesia on 28 September, turned around 430 hectares of land soft soil into mud across the central Sulawesi region in a process known as liquefaction.

O​fficials said that 2,103 people were killed and 3,500 homes destroyed. A further 5,000 people remain unaccounted for in the neighbourhoods swallowed by the mud.

Officials said that the Palu neighbourhoods of Balaroa, Petobo, and Jono Oge cannot be redeveloped due to the damage suffered.

Victims of Indonesia's Tsunami in 2018 Show all 23 1 /23 Victims of Indonesia's Tsunami in 2018 Victims of Indonesia's Tsunami in 2018 Photojournalist Paddy Dowling traveled with UK based charity Muslim Aid to the disaster areas of North Sulawesi to witness the scale of Indonesia’s earthquake & tsunami. In this photo a man sifts through the rubble of his home close to Darul Muttaqien Mosque in Palu. When the earthquake struck he was not there he was out with his family. “Thank god we are all fine” Paddy Dowling Victims of Indonesia's Tsunami in 2018 Lewi Kai 44 sat and waited for news of his wife next to the building that collapsed on her as a result of the earthquake in North Sulaawesi. Rescue workers rotating in shifts around the clock to recover her body Paddy Dowling Victims of Indonesia's Tsunami in 2018 Darul Muttaqien Mosque was the heart of the community for many here in Palu. Many victims were inside their homes or at the mosque when the quake struck at around 1800hrs. Magareb prayer for many muslims here was their final prayer Paddy Dowling Victims of Indonesia's Tsunami in 2018 A young boy is dragged from the earth where JL Kenanga street once existed and placed in an orange body bag to be carried to a mass grave in Palu Paddy Dowling Victims of Indonesia's Tsunami in 2018 Many vehicles in Palu due to the quake were lifted from their original location. The owner of this pickup pointing to over 50 feet from where it was last parked Paddy Dowling Victims of Indonesia's Tsunami in 2018 Residents of an IDP camp in Donggala queue for food distribution in an old disused open air theatre. Local NGOs are doing fantastic work here in Indonesia with this crisis however the road to help the victims of this disaster is a long one. Muslim Aid is the only British NGO delivering aid out in Palu through local partners Paddy Dowling Victims of Indonesia's Tsunami in 2018 SARS workers drill through reinforced concrete in a collapsed building in Palu. The build is unstable so they must work fast to recover the last body in the floor below Paddy Dowling Victims of Indonesia's Tsunami in 2018 Military soldiers work tirelessly in the searing heat to recover and bury the dead here in Palu. A familiar silhouette, In pairs they carry members of the community to their final resting place Paddy Dowling Victims of Indonesia's Tsunami in 2018 Two young men in Palu sift through the rubble in front of their home. They salvage as much wood as they could tying it into bundles to store as firewood for fuel to use cooking in the kitchen Paddy Dowling Victims of Indonesia's Tsunami in 2018 The rows of body bags zipped up and lined up here in Palu is rising daily. JL Kenanga street in Palu is where locals say hundreds of bodies may still be buried under the rubble Paddy Dowling Victims of Indonesia's Tsunami in 2018 A body recovered from Perumnas Baloroa in Palu lay on the road outside the morgue in the blistering heat of the day. The smell of death is everywhere here in Palu Paddy Dowling Victims of Indonesia's Tsunami in 2018 Military soldiers take refreshment and shade under a tree as they watch the digger recover the dead of Paul and Donggala Paddy Dowling Victims of Indonesia's Tsunami in 2018 Bubba, 65, has waited patiently for eight days for news of his missing son feared buried below the rubble Paddy Dowling Victims of Indonesia's Tsunami in 2018 SARS teams exit a building in Palu metres from the destroyed of Ramayana shopping Mall. They are searching for a body of a woman still unaccounted for. Her husband waits by for news nearby Paddy Dowling Victims of Indonesia's Tsunami in 2018 An young Indonesian soldier is drafted up from Makassar in South Sulawesi to help during this national disaster. He had formally been posted to Sudan before arriving in Palu. He joins his team searching for the dead and taking them to the mass graves nearby Paddy Dowling Victims of Indonesia's Tsunami in 2018 Excavators work tirelessly digging through the earth to recover the bodies of this tragedy grinding through rock, mud and metal. Many locals lucky enough to survive watch heavy hearts as each corpse is placed into a body bag Paddy Dowling Victims of Indonesia's Tsunami in 2018 Residents of the district of Petobo in Palu wait behind a military cordon as the excavations continue in the distance. They wait in hope for news of the missing Paddy Dowling Victims of Indonesia's Tsunami in 2018 Residents return to sift through the rubble to salvage what they can of their belongings and the fabric of their homes such as corrugated tin and timber which can be used to build a temporary shelter elsewhere Paddy Dowling Victims of Indonesia's Tsunami in 2018 35 bodies excavated in a single afternoon alone in Palu in the shadows of Darul Muttaqien Mosque Paddy Dowling Victims of Indonesia's Tsunami in 2018 The level of destruction in Palu caused by the earthquake on 28th September resembled a scene from an apocalyptic film Paddy Dowling Victims of Indonesia's Tsunami in 2018 Public donations of food, bottled water and clothing arrives at Siding Hajj Home IDP Camp in Makassar. Indonesia’s newest IDP camp which will home around10,000 people now homeless Paddy Dowling Victims of Indonesia's Tsunami in 2018 Military soldiers work tirelessly in the searing heat to recover and bury the dead here in Palu. A familiar silhouette, In pairs they carry members of the community to their final resting place Paddy Dowling Victims of Indonesia's Tsunami in 2018 Residents from the district of Petobo in Palu, saw houses, trees and cars disappear under the ground due to liquefaction. There is a 3km area for the diggers to excavate. To see more of Paddy's work please visit his website www.paddydowling.co.uk Paddy Dowling

Balaroa and Petobo will be turned into green spaces with monuments dedicated to the disaster's victims.

Rescue workers had managed to retrieve the body of his wife, Hastuti, who was found still holding the bodies of their other two daughters, aged four and two.

"It is impossible to rebuild homes in the original places," public works and housing minister Basoeki Hadimoeljono told reporters earlier this week.

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The Indonesian government is considering a 6 trillion rupiah (£302m) plan to invest in a "New Palu City".

The World Bank has said it can provide the country up to £757m in loans for reconstruction and improving disaster preparednesses.

A massive effort is underway to distribute 215 tonnes of relief, including tarpaulins and clean drinking water, to the thousands of people displaced by the disaster, before the start of the monsoon rains, the Indonesian Red Cross said.