Eleven Indonesian fishermen have been rescued from a desert island in the Indian Ocean after their vessel shipwrecked during a powerful cyclone, Australian authorities say.

They had been stranded for six days  without food and water.

Eight fishermen remained missing, the Australian Maritime Safety Authority (AMSA) said on Wednesday.

The survivors were rescued on Monday night from Bedwell Island, about 313km west off the coast of the town of Broome in Western Australia state.

A border security aircraft spotted them during a surveillance mission following Cyclone Ilsa, which smashed into Australia's northwest as a category 5 storm last week, setting new wind speed records.

They were then moved to Broome and given necessary medical care, an AMSA spokesperson said in a statement.

The fishermen informed authorities that two vessels had been caught in the cyclone, one with 10 crew and the other with nine.

The ship with 10 crew washed ashore at Bedwell Island but the second vessel sank in bad weather, AMSA said.

One person from the missing vessel spent 30 hours in the water before also being washed ashore at Bedwell Island, a small sandy cay within the Clarke Reef coral atoll.