China has deployed 10 satellites to help in the massive air and sea search for a missing Malaysian airliner, the People's Liberation Army Daily said on Tuesday.

The satellites will use high-resolution earth imaging capabilities, visible light imaging and other technologies to "support and assist in the search and rescue operations for the Malaysian Airlines aircraft", the newspaper said in an article that was also carried on the defence ministry's website.

Dozens of ships and aircraft from 10 countries scoured the seas around Malaysia and south of Vietnam as questions mounted over possible security lapses and whether a bomb or hijacking attempt could have brought down the Boeing 777-200ER which took off from the Malaysian capital, Kuala Lumpur.

China has urged Malaysia to speed up the search for the plane. About two-thirds of the 227 passengers and 12 crew now presumed to have died aboard the plane were Chinese.

The Chinese satellites will also help in weather monitoring, communication and search operations in the area where the plane disappeared, the newspaper said.

China will also strengthen the Beidou navigation system's satellite monitoring capabilities to "provide reliable navigation for the rescue operations and communication support".

Meanwhile, investigators in Malaysia are voicing skepticism that the airliner that disappeared early Saturday with 239 people on board was the target of an attack, US and European government sources close to the probe said.

Neither Malaysia's Special Branch, the agency leading the investigation locally, nor spy agencies in the US and Europe have ruled out the possibility that militants may have been involved in downing Malaysia Airlines Flight MH370.

But Malaysian authorities have indicated that the evidence so far does not strongly back an attack as a cause for the aircraft's disappearance, and that mechanical or pilot problems could have led to the apparent crash, the US sources said.

"There is no evidence to suggest an act of terror," said a European security source, who added that there was also "no explanation what's happened to it or where it is."

Interpol confirmed on Sunday at least two passengers used stolen passports and said it was checking whether others aboard had used false identity documents.

Even so, one US source said Malaysian authorities were leaning away from the theory that the plane was attacked. Their view was mostly based on electronic evidence that indicates the flight may have turned back toward the Malaysian capital of Kuala Lumpur before disappearing.

Even that information has not been clearly confirmed, and investigators and intelligence sources say the fate of the Flight MH370 is still shrouded in mystery.

One reason was that the aircraft had failed to make automatic contact with a flight data-monitoring system after vanishing from radar screens, two people familiar with the matter said on Monday. Such contact could have helped investigators determine what happened.

The aircraft was equipped with a maintenance computer capable of talking to the ground automatically through short messages known as ACARS. "There were no signals from ACARS from the time the aircraft disappeared," a source involved in the investigations said.

Also raising doubts about the possibility of an attack, the US extensively reviewed imagery taken by spy satellites for evidence of a mid-air explosion, but saw none, a US government source said. The source described US satellite coverage of the region as thorough.

With no success so far, authorities were planning to widen the search from Tuesday, Azharuddin Abdul Rahman, the head of Malaysia's Civil Aviation Authority, told reporters on Monday.

"Unfortunately we have not found anything that appears to be objects from the aircraft, let alone the aircraft," he said. "As far as we are concerned, we have to find the aircraft. We have to find a piece of the aircraft if possible."

Azharuddin said a hijacking attempt could not be ruled out as investigators explore all theories.

A senior police official told Reuters that people armed with explosives and carrying false identity papers had tried to fly out of Kuala Lumpur in the past, and that current investigations were focused on two passengers who were on the missing plane with stolen passports.

"We have stopped men with false or stolen passports and carrying explosives, who have tried to get past KLIA (airport) security and get on to a plane," he said. "There have been two or three incidents, but I will not divulge the details."

Azharuddin also said the two men with stolen passports did not look like Asians, but he did not elaborate. Airport CCTV footage showed they completed all security procedures, he said.

"We are looking at the possibility of a stolen passport syndicate," he said.

About two-thirds of the 227 passengers and 12 crew now presumed to have died aboard the plane were Chinese. The airline said other nationalities included 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans. - Reuters