A spokeswoman for the Joint Agency Co-ordination Centre, headed by former Defence chief Angus Houston, said the overall search area remained at 46,713 square kilometres, as the JACC advised earlier on Friday morning.

"That hasn’t changed," the spokeswoman said in response to questions about the veracity of Mr Abbott’s comments.

She said the latest information on the status of the search was contained in a statement from the JACC. She would not define the specific search area for the black boxes.

In an address to a lunch in Shanghai on Friday, Mr Abbott said the search area had been narrowed.

"We are confident that we know the position of the black box flight recorder to within some kilometres," he said.

"Still, confidence in the approximate position of the black box is not the same as recovering wreckage from almost four-and-a-half kilometres beneath the sea or finally determining all that happened on that flight.

"Earlier on Friday, the JACC sent out a statement saying the search area still covered over 45,000 square kilometres of ocean.

"Today the Australian Maritime Safety Authority has planned two search areas in close proximity totalling about 46,713 square kilometres," the statement read.

"The centre of the search area lies approximately 2312 kilometres north-west of Perth."

Mr Abbott told a press conference in China he was increasingly confident that signals received in the search for MH370 were from the plane’s black boxes.

He spoke shortly after The West Australian aviation editor Geoffrey Thomas set social media alight by tweeting: "Black boxes of MH370 may have been found. PM to make announcement at 11.45am [Perth time, 1.45pm AEST]."

However, the man in charge of the search, Air Chief Marshal Angus Houston (Ret’d), subsequently said no major breakthrough had occurred.

The comments from Mr Abbott are considered significant given he has been particularly cautious when addressing questions on the missing Boeing jet during his week-long visit to north Asia.

They came just hours before he was due to meet Chinese President Xi Jinping for a state dinner in Beijing.

Mr Abbott said a "series of detections" from the towed pinger aboard the ADV Ocean Shield had enabled authorities to narrow the search area significantly, but that they were racing against the clock before the black box batteries died.

"We’re very confident the signals we’re detecting are from the black box from MH370," he told reporters.

"We’re hoping to get as much information as we can before the signal finally expires."

He said he would hold back on announcing more information before he briefed President Xi on the latest findings, out of respect for the families of the more than 150 Chinese passengers on the flight.

Shortly after Mr Abbott’s press conference, Mr Houston revealed that an initial assessment of the possible signal detected by a RAAF AP-3C Orion aircraft on Thursday afternoon had been determined as not related to an aircraft underwater locator beacon.

“On the information I have available to me, there has been no major breakthrough in the search for MH370. I will provide a further update if, and when, further information becomes available," Mr Houston said.

And he gave no indication that the black boxes were any closer to being found.

- with Philip Wen, Mark Kenny, Conal Hanna, Megan Levy and Amanda Hoh