However no further signals have been detected in the search for missing flight MH370 and time on the plane’s black boxes is running out.

On Saturday Mr Abbott told reporters in Beijing that although Australian authorities had "a high degree of confidence" the transmissions detected by ADV Ocean Shield were from flight MH370's black box, they still faced an incredibly difficult task ahead.

"Yes, we have narrowed down – very considerably narrowed down – the search area," he said. "But trying to locate anything 4.5 kilometres beneath the surface of the ocean, about 1000 kilometres from land is a massive, massive task and it is likely to continue for a long time to come."

Mr Abbott said the signal was "rapidly fading" and search crews were scrambling to detect further pings to narrow the search zone before time ran out.

"Once that's been done –and I don't want to speculate on when that might be – once that's been done it's our intention to then deploy the submersible which will conduct a sonar search of the seabed and based on the sonar search attempt to get a visual on wreckage."

By air and sea, search crews scoured a remote area of the Indian Ocean about 41,393 square kilometres in size, the centre of the range located about 2331 kilometres north-west of Perth, on Saturday.

As many as nine military aircraft, a civilian jet and 14 ships were tasked with the day’s search.

By Saturday morning, the Australian Maritime Safety Authority had narrowed the overall search area overnight to 41,393 square kilometres from Friday’s search area of 46,713.

But the size of the underwater search zone for the black box, being investigated by ADV Ocean Shield, HMS Echo and RAAF aircraft, to the north of the overall search range, had not previously been released.

After a US pinger locator being towed by ADV Ocean Shield detected two signals consistent with an aircraft black box on April 5, the ship started performing a slow, square sweep of an area about 1800 metres long.

A week has passed since the Ocean Shield began narrowing its square; and two more signals were detected on Tuesday, which would most  likely have also affected its target range.

There have been no confirmed signal detections in the past 24 hours, the search’s Joint Agency Co-ordination Centre said in a statement on Saturday morning.

"Ocean Shield continues more focused sweeps with the Towed Pinger Locator to try and locate further signals related to the aircraft’s black boxes," JACC stated.