At least 34 people have been killed and more than 600 injured after a magnitude 6.2 earthquake struck and toppled buildings in Indonesia’s Sulawesi island in the early hours of Friday, according to authorities.

The epicentre of the quake was six kilometres (3.73 miles) northeast of the city of Majene, at a depth of 10 kilometres (6.2 miles).

“Authorities in west Sulawesi are still working to restore communications. Electricity is down. Once communications are restored we should have a clearer picture of the exact extent of the damage,” she said.

“So far we know that eight people are confirmed dead in the city of Majene, 26 in the nearby city of Mamuju. There are 10 evacuation centers set up in the city of Majene and five in the city of Mamuju.”

President Joko Widodo offered condolences to the victims in a video statement, urging people to stay calm and authorities to step up search efforts.

Residents inspect earthquake-damaged houses in Mamuju, West Sulawesi, Indonesia on Friday [Rudy Akdyaksyah/AP]

At least 15,000 people have been displaced following the quake.

North of Majene, more than a dozen patients and staff are trapped beneath the rubble of a hospital that was flattened by the quake.

“The hospital is flattened – it collapsed,” said Arianto from the rescue agency in Mamuju city, who goes by one name.

“There are patients and hospital employees trapped under the rubble and we’re now trying to reach them,” he told AFP news agency, without giving a specific figure.

Images and videos posted online showed damaged buildings and several people trapped in collapsed structures.

The disaster mitigation agency said a hotel and the office of the West Sulawesi governor were also severely damaged, and electricity supplies were also down.

Some roads and bridges were also damaged slowing down the rescue operation.