A man surveys the damage caused by earthquake and tsunami in Palu, Central Sulawesi, Indonesia. Picture: Rifki/AP

Jakarta - Many bodies were found on Saturday along the shoreline of the Indonesian city of Palu on Sulawesi island which was hit by a major earthquake and tsunami, as the death toll rose to 48 people, authorities said.

Strong aftershocks continued to rock the coastal city on Saturday morning after waves up to three metres (9.8 feet) high swept through the scenic tourist town, triggered by a 7.5 magnitude earthquake on land.

"Many bodies were found along the shoreline because of the tsunami, but the numbers are still unknown," said Sutopo Purwo Nugroho, spokesman of Indonesia's disaster mitigation agency BNPB said in news briefing in Jakarta.

At least 48 people had been killed and the death toll was expected to rise, said Nugroho.

Amateur footage shown by local TV stations, which could not immediately be authenticated by Reuters, showed waters crashing into houses along Palu's shoreline, scattering shipping containers and flooding into a mosque in the city.

Nugroho described the damage as "extensive" with thousands of houses, hospitals, shopping malls and hotels collapsed and a bridge washed away.

A car swept away by a tsunami is seen stuck under a damaged building in Palu, Central Sulawesi. Picture: Dede Budiyarto via AP

Bodies of victims trapped between the rubble of collapsing buildings were also found, he said, adding that more than 350 people were injured.

Dozens of injured people were being treated in makeshift medical tents set up outdoors, TV images showed.

Indonesia's meteorological and geophysics agency BMKG issued a tsunami warning after the quake, but lifted it 34 minutes later. The agency was widely criticised for not informing a tsunami had hit Palu on Saturday, though officials said waves had come within the time the warning was issued.

The quake and tsunami caused a major power outage that cut communications around Palu and on Saturday authorities were still having difficulties coordinating rescue efforts.

BNPB has not been able to get any information from the town of Donggala, closer to the epicentre of the quake 27 km (16 miles) away. More than 600,000 people live in Donggala and Palu.

Chief security minister Wiranto told TVOne the military had started sending in cargo planes from the capital Jakarta carrying relief aid.

The city's airport remained closed after its runway and air traffic control tower was damaged in the quake but officials said they were preparing to reopen to allow aid to come in.

The ruin of a mosque badly damaged by earthquake and tsunami is seen in Palu, Central Sulawesi. Picture: Rifki/AP

"We hope the airport can be reopened soon for flights carrying disaster relief and aid," said Yohannes Sirait of AirNav, the air traffic management agency.

Road access to Palu from the east and the south are disconnected, making relief efforts difficult, authorities said.

"There is no evacuation yet in the disaster area," Tezar Kodongan, a Palu resident, told Metro TV.

The Palu area was hit by a less powerful quake earlier on Friday, which destroyed some houses, killed one person and injured at least 10 in the fishing town of Donggala, closest to the epicentre, authorities said.

The U.S. Geological Survey put the magnitude of the second quake at a strong 7.5, after first saying it was 7.7.

Indonesia sits on the Pacific Ring of Fire and is regularly hit by earthquakes. In August, a series of major quakes killed over 500 people in the tourist island of Lombok and destroyed dozens of villages along its northern coast.

Palu was hit by tsunami in 1927 and 1968, according to BNPB.