Magnitude 7.5-quake launches tsnunami into Indonesian city of Palu with deaths and injuries unknown.

The Indonesian island of Sulawesi was slammed by a tsunami set off by a powerful earthquake that wiped out buildings, but it was unclear the severity of deaths and injuries.

Indonesian disaster agency spokesman Sutopo Purwo Nugroho said on Friday the magnitude 7.5 earthquake caused the tsunami that hit the provincial capital of Palu and a smaller city of Donggala.

“There are reports that many buildings collapsed in the earthquake,” Sutopo said in a statement.

He said communications with the area in central Sulawesi were down and the search-and-rescue effort was being hampered by darkness.

There were no immediate reports of deaths or injuries.

Sutopo said in a live TV interview that houses were swept away and families are reported missing.

The city, with a population of 350,000, was about 80km from the quake’s epicentre. The US Geological Survey said the shallow quake was centred at a depth of 10km.

Dramatic video footage filmed from the top floor of a parking ramp spiral in Palu showed a churning wall of whitewater mow down several buildings and inundate a large mosque.

Pictures supplied by the disaster agency showed a badly damaged shopping mall in Palu where at least one floor had collapsed onto the storey below.

Other pictures showed major damage to buildings with rubble strewn about the road and large cracks running through pavement.

Mirza Arisam, a resident of Kendari, the capital of neighboring Southeast Sulawesi, said his uncle and his family of five, including three children, were holidaying in Palu and unable to be contacted after the tsunami.

The disaster agency released a photo showing a heavily damaged shopping mall [BNPB/AFP]

Central Sulawesi was hit earlier on Friday by a magnitude 6.1 earthquake.

“All the things in my house were swaying and the quake left a small crack on my wall,” Donggala resident Mohammad Fikri said by telephone.

Officials asked people to remain alert as a number of moderate aftershocks hit.

“We advise people to remain in safe areas and stay away from damaged buildings,” Supoto said.

He also said the national agency in the capital Jakarta was having difficulties reaching authorities in the affected area.

Supoto said there was “much damage” in the Donggala area – home to about 300,000 people – where the first quake hit.

A series of earthquakes in July and August killed nearly 500 people on the holiday island of Lombok, hundreds of kilometres southwest of Sulawesi.

Indonesia sits on the Pacific Ring of Fire, an arc of volcanoes and fault lines in the Pacific Basin that is prone to earthquakes.

In 2004, an earthquake off the northern Indonesian island of Sumatra triggered a tsunami across the Indian Ocean, killing 226,000 people in 13 countries, including more than 120,000 in Indonesia.