The number of people known to have died in Indonesia in Friday's earthquake and tsunami has risen to more than 1,200, the country's disaster response agency says.

The death toll jumped on Tuesday from a previous confirmed figure of 844.

The 7.5-magnitude quake struck just off the central island of Sulawesi, setting off a tsunami that engulfed the coastal city of Palu.

People there are growing increasingly desperate for food, fuel and water.

Humanitarian relief convoys entering the city are now being escorted by soldiers and police.

And there are fears some survivors may still be trapped under the rubble of buildings.

Are there still hopes for finding survivors?

Indonesian Red Cross officials have told the BBC that the bodies of 34 Indonesian students were found under a church buried by a mudslide.

They were among a group of 86 students reported missing from a Bible camp in the Jonooge Church Training Centre. The whereabouts of the other 52 students are not known.

"The mud conditions in that area are terrible, we have to walk about 1.5 hours to reach [the mudslide area], that makes it very difficult," Ridwan Sobri, a spokesperson for the Indonesian Red Cross told the BBC.

Mr Sobri said the identities and ages of the students could not yet be confirmed.

Rescuers are also still hunting for survivors in the ruins of a four-storey hotel in the town.

An estimated 50 people were inside the Hotel Roa Roa when it collapsed. About 12 people have been recovered - only three came out alive.

This is what's left of the Roa Roa hotel in Palu -- Photo: REUTERS

"We have to be very careful so we don't risk hurting any survivors when we move the debris," the head of the rescue team, Agus Haryono, told Reuters.

Why are people struggling to get help?

Across Palu, blocked roads, a damaged airport and broken telecommunications have made it difficult to bring help into the affected area, and impossible to contact more remote regions.

With hospitals damaged, injured people have been treated in the open and at least one military field hospital has been set up.

The military has taken over the airport to fly aid in, and injured people and other evacuees out.

But for thousands of people wanting to get the first commercial flight out of Palu, the wait continues.

"I'd get a plane anywhere. I've been waiting for two days. Haven't eaten, barely had a drink," 44-year-old food vendor Wiwid told Reuters news agency.

On Monday, 3,000 to 5,000 people who wanted to evacuate from Palu swarmed the airport hoping to hitch a ride on a military Hercules plane. The military arranged for them to depart on ferries instead.

Hercules planes are used to evacuate the injured who are in urgent need of medical treatment.

The charity Save the Children says many of the children in Palu "will have experienced unimaginable trauma and distress".

"Losing their mother or father, and watching everything they have known washed away," said the charity's Tom Howells.

Many people are having to sleep in makeshift shelters or on the street, with little access to food, medication or emotional support, added Mr Howells.

A mass grave in Palu -- Photo: REUTERS

Across the city, mass graves are being dug.

Why was the disaster so bad?

The 7.5-magnitude quake occurred at a depth of 10km (6.2 miles) just off the central island of Sulawesi at 18:03 (10:03 GMT) on Friday, setting off a tsunami.

The earthquake was powerful but shallow and with more lateral than vertical movement, not typically the kind of tremor that sets off tsunamis.

Vice-President Jusuf Kalla has said the final death toll could be in the thousands while the Red Cross estimates that more than 1.6 million people have been affected.

Source: BBC