Four Australians have been released from hospital after they were caught in a ferry explosion in Indonesia.

The four were injured along with other tourists when small explosions rocked a ferry crossing between popular islands Bali and Lombok on Friday afternoon, officials say.

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It is believed the explosions came from the fuel tank of the ferry, which was carrying 129 passengers.

The boat was about one-third into its journey to the resort island of Bali from Senggigi in Lombok when it burst into flames.

The Department of Foreign Affairs confirmed four Australians were admitted to hospital but then released.

Passengers from France, Italy, US and New Zealand were among the injured.

“No one has serious injuries. Most of the 25 patients suffered minor injuries from the impact,” an official at West Nusa Tenggara hospital, Oxy Cahyo Wahyuni, said.

Local water police official Khoirul Anwar said: “Two explosions hit the vessel 30 minutes after it set off from Senggigi, with the second explosion breaking the windows and hitting the passengers.

“We suspected that the explosion came from the fuel tank.”

Local police are investigating the cause of the explosions, he said.

– AFP