An Australian P-3C Orion reconnaissance plane has spotted "something" in the waters off Pangkalan Bun near central Kalimantan where a massive air-sea search has been mounted for AirAsia Indonesia flight QZ8501, it was reported.

Indonesian Commando Chief Marshall Dwi Putranto said that the Royal Australian Air Force (RAAF) plane detected the object some 160km south-west of Pangkalan Bun, Malaysian Insider reported on Monday, citing Indonesia's Detiknews website.

That is about 1,120km from the last known location of the Airbus A320-200 that went missing on Sunday.

Dwi was quoted as saying that authorities did not know what the object was and aircraft had been despatched to the location.