Objects sighted at sea on Sunday by an Australian Orion searching for missing Malaysia Airlines flight MH370 have been identified as fishing buoys, nets and other ocean junk.

The crew of a P-3 Orion captained by Flight Lieutenant Russell Adams reported at least four orange objects, each more than two metres in size, during an 11-hour mission over the Australian search zone, west of Perth, on Sunday.

"We were able to detect many objects in the water today," Flight Lieutenant Adams said on the tarmac at RAAF Pearce on Sunday.

"We were able to rule a few out as fishing buoys and fishing nets, however, of interest today we did encounter an area within approximately five nautical miles which included at least four orange coloured objects greater than approximately two metres in size each.”