Local government official Samuel Pekulimu says 83 migrants _ including 15 women and 12 children _ were in police custody after being found Monday stranded on Salura off Sumba island in East Nusatenggara province.
Nikolaus Salo, an activist for illegal migrants, said authorities on Flores island detained another 40 Afghans found on nearby Babi.
The Afghan illegal migrants were found by Indonesian authorities without proper travel documents but officials confirmed they were bound for Australia to seek asylum.
Australia has become a popular destination for asylum-seekers from Afghanistan and Sri Lanka. Most of the illegal migrants use Indonesian islands as their pick-up points on their way to Australia.
Last year some 255 ethnic Tamil asylum-seekers from Sri Lanka on board a wooden boat bound for Australia were held in Indonesia.
Australia has received 1,650 refugees from January to October last year and about a thousand more were being processed in Christmas Island, found in the Indian ocean between Australia and Indonesia.