The co-pilot of the missing Malaysian airliner MH370 tried to make a mid-flight call from his mobile phone just before the plane vanished from radar screens, according to Malaysian newspaper reports.

The call ended abruptly possibly "because the aircraft was fast moving away from the [telecommunications] tower," the New Straits Times quoted a source as saying.

However, the Malaysian daily also quoted another source saying that while Fariq Abdul Hamid's "line was reattached", there was no certainty that a call was made from the Boeing 777 which vanished on 8 March.

The report - titled a "desperate call for help" - did not say who the co-pilot was trying to contact.

Fariq and Captain Zaharie Ahmad Shah have come under intense scrutiny after the plane mysteriously vanished en route from Kuala Lumpur to Beijing with 239 people on board.

Investigators indicated last month that the flight was deliberately diverted and its communication systems manually switched off as it was leaving Malaysian airspace, triggering a criminal investigation by police that has revealed little of substance so far.

A number of theories have been put forward concerning the fate of MH370, including a hijacking, a terrorist attack or a rogue pilot.

There have been unconfirmed reports in the Malaysian media of calls made by the captain before or during the flight but so far no details have been released.

The NST report said that after turning off course MH370 flew low enough near Penang island on Malaysia's west coast for a telecom tower to pick up the co-pilot's phone signal.

The phone line was "reattached" between the time the plane veered off course and blipped off the radar, the government-controlled paper quoted the second source as saying.

"A 'reattachment' does not necessarily mean that a call was made. It can also be the result of the phone being switched on again."

Malaysia's transport ministry said it was examining the NST report and would issue a response.

However, Hishammuddin Hussein, the transport minister, appeared to quash the claim. "I cannot comment [on the newspaper report] because if it is true, we would have known about it much earlier," he told reporters.

"We received numerous leads and we followed them but unfortunately, it was a roller-coaster ride, whereby we received information and investigated [them] but they were baseless."

He said that throughout the search for the aircraft, he had not confirmed anything without corroboration or verification.

Meanwhile, the Australian prime minister, Tony Abbott, said signals picked up during the search in the remote southern Indian Ocean, believed to be "pings" from the black box recorders, were "rapidly fading".

"While we do have a high degree of confidence that the transmissions that we've been picking up are from flight MH370's black box recorder, no one would underestimate the difficulties of the task still ahead of us," Abbott told a news conference in Beijing.

Search officials say they are confident they know the approximate position of the black box recorder, although they have determined that the latest "ping', picked up by searchers on Thursday, was not from the missing aircraft.

Batteries in the black box recorder have already exceeded their normal 30-day life, making the search to find it on the murky seabed all the more urgent. Once they are confident they have located it, searchers then plan to deploy a small unmanned "robot", known as an Autonomous Underwater Vehicle.

"Work continues in an effort to narrow the underwater search area for when the Autonomous Underwater Vehicle is deployed," the Australian agency co-ordinating the search said on Saturday. "There have been no confirmed acoustic detections over the past 24 hours," it said in a statement.

The black box records data from the cockpit and conversations among flight crew and may provide answers about what happened to the plane, which flew thousands of miles off course after taking off.

The mystery has prompted the most expensive search and rescue operation in aviation history.

Malaysia's government has begun investigating civil aviation and military authorities to determine why opportunities to identify and track the flight were missed in the chaotic hours after it vanished.

Analysis of satellite data has led investigators to conclude the Boeing 777 crashed into the ocean somewhere west of Perth. So far, four "ping" signals, which could be from the plane's black box recorders, have been detected in the search area in recent days by a US Navy "Towed Pinger Locator".

"We are now getting to the stage where the signal, from what we are very confident is the black box, is starting to fade and we are hoping to get as much information as we can before the signal finally expires," Abbott said on Friday.

The US supply ship USNS Cesar Chavez has joined the Australian-led taskforce to provide logistics support and replenish Australian navy ships, a Pentagon spokesman said.

Up to nine military aircraft, one civil aircraft and 14 ships were scouring a 25,720 sq mile patch of desolate ocean some 1,445 miles northwest of Perth.

The extensive search and rescue operation has so far included assets from 26 countries.

Australia's Ocean Shield, which has the towed pinger locator on board, is operating in a smaller zone, just 230 sq miles about 1,040 miles north-west of Perth. That is near where it picked up the acoustic signals and where dozens of sonobuoys capable of transmitting data to search aircraft via radio signals were dropped on Wednesday.

Experts say the process of teasing out the signals from the cacophony of background noise in the sea is slow and exhausting.

An unmanned submarine named Bluefin-21 is on board the Ocean Shield and could be deployed to look for wreckage on the sea floor around 2.8 miles below the surface once a final search area has been identified.