A group of Indonesian fishermen are recovering after being shipwrecked on a coral atoll off Australia's west coast for six days without food or supplies, authorities said Wednesday.

Ten men washed up on Bedwell Island, about 300 kilometres (186 miles) west of the resort town Broome, after their boat was battered by a severe tropical cyclone while fishing in the Indian Ocean.

An eleventh fisherman from a second vessel also washed ashore after treading water for 30 hours -- but authorities fear his nine crewmates drowned after their boat sank in heavy seas.

Photos showed the castaways had fashioned a makeshift camp on the narrow spit of beach, salvaging what they could from their small vessel, which lay beached nearby.

Bedwell Island is remote, exposed and inhospitable -- little more than a bare stretch of white sand with no natural shelter or freshwater sources.

The castaways were winched off the island by a rescue helicopter on Monday evening after being spotted by an Australian Border Force surveillance plane on patrol.

They are now receiving medical treatment on the Australian mainland and will return to Indonesia once they have recovered, officials said.

"Upon their arrival on the mainland, the individuals were provided with the appropriate care and medical support," the Australian Maritime Safety Authority said in a statement.

Tropical Cyclone Ilsa made landfall in Western Australia on Friday last week, lashing coastal regions with some of the strongest winds the country has ever recorded.