JAKARTA, Indonesia (CNN) — Three days after a 7.5 magnitude earthquake and 3-meter-high (10 foot) waves crashed onto the Indonesian island of Sulawesi, the provincial capital of Palu, a city of 350,000, lies in ruins.

Dead bodies covered by tarps lined the city's streets over the weekend, exposed to Indonesia's blistering heat, as rescuers searched rubble for survivors buried in crumpled buildings.

Authorities will bury some of the 832 people confirmed dead in mass graves Monday to prevent the spread of disease, Brig. Gen. Dedi Prasetyo told Indonesian state media.

An estimated 2.4 million people were affected by the disaster, Indonesian Disaster Management Agency spokesman Sutopo Purwo Nugroho said. Hundreds were badly injured and at least 17,000 people left homeless.

Rescuers are still trying to reach the more isolated fishing towns of Donggala and Mamuju, two areas feared to be heavily devastated.

"The Indonesian Red Cross is racing to help survivors, but we don't know what they'll find there," said Jan Gelfand, who heads the International Red Cross delegation in Indonesia. "I don't think we've quite seen the worst of things yet."

The region has been essentially cut off from the outside world due to damaged roads and infrastructure, hampering rescue efforts.

Aid has been slow to trickle in, delayed by severe damage to Mutiara Sis Al Jufri Airport in Palu, which was closed for 24 hours after the tsunami but which has since reopened to limited flights.

Priority will be given to evacuating survivors and allowing aid workers to bring in food and fresh water, said Indonesia President Joko Widodo, who visited the disaster site on Sunday.

Images showed crowds of residents at the airport, waiting to board Hercules flights out of the area. Widodo has authorized the country to request international aid relief.

Conditions in the devastated city are grim.

Two days after the quake, as they waited for aid, survivors took matters into their own hands and entered shops, wheeling away trolleys filled with food and water.

Mia, 40, was at the Ramayana shopping mall in Palu with her daughters when the ground started shaking.

"I just finished my shopping and went to the cashier, suddenly everything got dark and the walls started falling around us, it was horrible," said Mia, who like many Indonesians only goes by one name. She said she ran down a broken escalator with her daughters. They made it out alive.

The earthquakes were just the start of the horror for residents of Palu and surrounding areas. The largest tremor, magnitude 7.5, triggered a tsunami that sent waves of "about three meters high" to the beaches of Palu and Donggala.

Homes, business and vehicles along the coast were washed away by the violent waves. Uprooted trees and pools of water could be seen throughout the area. Roads and bridges were destroyed.

Across the region, first responders continue to dig through the rubble, sometimes by hand, in the hopes of finding survivors who were trapped by the massive quake or the destructive tsunami that followed.

Workers scrambled Sunday to rescue about 50 people trapped beneath the debris of the Roa Roa hotel.

Aerial images showed the eight-floor building completely collapsed, and video Nugroho showed orange-clad responders carrying an individual on a stretcher through the rubble.

Seventy-one foreigners were in Palu at the time of the quake and most were safely evacuated to Jakarta. At least five foreigners, including three French nationals as well as a Malaysian and a South Korean national, are unaccounted for, he said.

As of Sunday, there were no reports of U.S. citizens affected in the quake, the U.S. Embassy in Jakarta told CNN.

'Are you ready?'

Bambang Soesatyo, speaker of the People's Representative Council and a member of Golkar Party, told reporters Sunday the government needs to increase the scale of relief operations in the affected area.

Many people had to sleep on the side of the road and many patients were treated in open spaces. Residents are still worried about aftershocks and are afraid to return home, said Soesatyo.

Hundreds of families are already mourning the loss of their loved ones, including an air traffic controller who's been hailed as a hero.

Anthonius Gunawan Agung, 21, died in the hospital after he jumped off the traffic control tower at the Palu airport when he thought the tower was collapsing.

He stayed behind to make sure a passenger airplane safely took off, according to AirNav Indonesia, the agency that oversees aircraft navigation.

The current and former mayor of Palu are also among the dead, according to the the Red Cross.

An early tsunami warning had been issued by the Indonesian meteorological agency, but was later lifted after the agency ascertained that the water had receded.

The quakes come weeks after a trio of earthquakes hit several islands in the South Pacific and Indonesia, including Lombok, which is still recovering from the effects of an August 5 earthquake that killed more than 430 people.

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