Australian Prime Minister Tony Abbott said on Sunday that small pieces of debris were spotted in the southern Indian Ocean, but he added cautiously that it was too early to confirm their linkage to the missing Malaysia Airlines MH370 flight.

Abbott announced the latest update on the ongoing search before leaving Papua New Guinea Sunday morning.

"Yesterday, one of our civilian search aircraft got visuals of a number of objects in a fairly small area in the overall Australian search zone," he told reporters.

He said that a wooden pallet was among the spotted items.

In the meantime, he warned that it was too early to draw too firm a conclusion.

"Obviously before we can be too specific about what it might be, we need to recover this material. It's still too early to be definite," he said.

The prime minister also mentioned that on Sunday, four more aircraft, two from China and two from Japan, will join the search.

Regarding the new satellite imagery released Saturday by China, he said that it suggests at least one large object.

He said that there is increasing hope that the authorities might solve the mystery of the missing aircraft.