Update | Australian PM's confidence over black box signals from MH370 rejected by search chief

Australian Prime Minister Tony Abbott expressed optimism over the hunt for missing flight MH370 during an official visit to China yesterday - despite the search chief's insistence there had been no new breakthrough.

Abbott said after attending a luncheon in Shanghai: "We have very much narrowed down the search area and we are very confident that the signals we are detecting are from the black box on MH370."

He said the hunt was focused on a narrow zone in the southern Indian Ocean and officials "knew the position of the black box flight recorder to within some kilometres", Xinhua reported.

Abbott, who later met President Xi Jinping in Beijing, warned that recovering the flight data and cockpit voice recorders would still be a "long, slow and painstaking process".

Abbott's optimism was in contrast to comments from the head of the agency co-ordinating the search effort, retired air chief marshal Angus Houston.