Malaysia's acting transport minister has said that reports that the missing Malaysian airplane flew for a number of hours are "inaccurate".

Hishammuddin Hussein's comments come after the Wall Street Journal reported that US investigators suspect the aircraft flew for about four hours after reaching its last confirmed location.

Speaking at a press conference in Kuala Lumpar, Mr Hussein also said satellite images released are not plane debris in the South China Sea. 

Mr Hussein said that China had told Malaysia the satellite photos were released "by mistake and did not show any debris".

Meanwhile, China has put pressure on Malaysia to improve its coordination over the search for the Boeing 777, which disappeared early on Saturday on a flight from Kuala Lumpur to Beijing.

Of the 239 people on board, up to 154 were Chinese.

Premier Li Keqiang demanded that the "relevant party" step up coordination, while China's civil aviation chief said he wanted a "smoother" flow of information from Malaysia.

Malaysia authorities have come under heavy criticism for their handling of the disaster.

Vietnamese and Malaysian planes scanned waters where a Chinese government agency website said a satellite had photographed three "suspicious floating objects" on Sunday.

The location was close to where the plane, Flight MH370, lost contact with air traffic control.

Aircraft repeatedly circled the area over the South China Sea but were unable to detect any objects, said a Reuters journalist, who was on board one of the planes.

It was the latest in a series of false signals given to the multi-national team that has been searching 27,000 square nautical miles (93,000 square km), an area the size of Hungary, for the Boeing 777-200ER.

Yesterday, Malaysia's air force chief said military radar had traced what could have been the jetliner to an area south of the Thai holiday island of Phuket, hundreds of miles to the west of its last known position.

His statement followed a series of conflicting accounts of the flight path of the plane, which left authorities uncertain even which sea to search in for Flight MH370.

The last definitive sighting on civilian radar screens came shortly before 1.30am on Saturday, less than an hour after the plane took off from Kuala Lumpur, as it flew northeast across the mouth of the Gulf of Thailand.

What happened next remains a mystery and the differing accounts put out by various Malaysian officials have drawn criticism of their handling of the crisis.

Malaysia Air Force chief Rodzali Daud told a news conference yesterday that an aircraft was plotted on military radar at 2.15 am, 320km northwest of Penang Island off Malaysia's west coast at the northern tip of the Strait of Malacca.

But there has been no confirmation that the unidentified plane was Flight MH370, he said.

Malaysia was sharing the data with international civilian and military authorities, including those from the United States.

"We are corroborating this," he added. "We are still working with the experts."

According to the data cited by the air force chief, if the radar had spotted the missing plane, the aircraft would have flown for 45 minutes and dropped only about 1,500 metres in altitude since its sighting on civilian radar in the Gulf of Thailand.

There was no word on which direction it was then headed, but if this sighting was correct, the plane would have turned sharply west from its original course, travelling hundreds of miles over the Malay Peninsula from the Gulf of Thailand to the Andaman Sea.

This would put it about 320km northwest of Penang, in the northern part of the Strait of Malacca, roughly south of Phuket and east of the tip of Indonesia's Aceh province and India's Nicobar island chain.

Indonesia and Thailand have said their militaries detected no sign of any unusual aircraft in their airspace. Malaysia has asked India for help in tracing the aircraft and New Delhi's coastguard planes have joined the search.