A tsunami up to two metres high hit a small city on the Indonesian island of Sulawesi this evening after a major 7.5 quake struck offshore, collapsing buildings and washing a vessel ashore, but officials could provide no information on casualties.

The quake hit as dusk fell and communications were down and the airport was closed, making it impossible to assess the damage to life and property, officials said.

National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said communications had been cut both in the city of Palu, a sleepy but growing tourist resort, and the nearby fishing town of Donggala, closest to the epicentre of the quake 80km away. More than 600,000 people live in Palu and Donggala.

Officials hope to be able to gauge the scale of the damage at daybreak after the strongest of a series of earthquakes that continued late into the evening.

"The 1.5- to two-metre tsunami has receded," Dwikorita Karnawati, who heads Indonesia's meteorology and geophysics agency, BMKG, told Reuters. "It ended. The situation is chaotic, people are running on the streets and buildings collapsed. There is a ship washed ashore."

BMKG had earlier issued a tsunami warning but lifted it within the hour.

Amateur footage shown by local TV stations, which could not immediately be authenticated by Reuters, showed waters crashing into houses along Palu's shoreline.

The national search and rescue agency will deploy a large ship and helicopters to aid with the operation, said agency chief Muhammad Syaugi, adding that he had not been able to contact his team in Palu.

Palu, hit by a 6.2 magnitude quake in 2005 which killed one person, is a tourist resort at the end of a narrow bay famous for its beaches and water sports.

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.

After the latest series of earthquakes, some people took to Twitter saying they could not contact their loved ones. "My family in Palu is unreachable," Twitter user @noyvionella said.

Palu airport was closed. The area was hit by a lighter quake earlier in the day,

which destroyed some houses, killing one person and injuring at least 10 in Donggala, authorities said.

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

"The (second) quake was felt very strongly, we expect more damage and more victims," Nugroho said.

Indonesia sits on the Pacific Ring of Fire and is regularly hit by earthquakes.

A series of earthquakes in July and August killed nearly 500 people on the holiday island of Lombok, off the island of Bali.

– Reuters