A Malaysia Airlines flight carrying 227 passengers and 12 crew went missing over the South China Sea on Saturday, presumed crashed, as ships from countries closest to its flight path scoured a large search area for any wreckage.

Vietnamese state media, quoting a senior naval official, had reported that the Boeing 777-200ER flight from Kuala Lumpur to Beijing had crashed off south Vietnam, but Malaysia's transport minister later denied any crash scene had been identified.

"We are doing everything in our power to locate the plane.

We are doing everything we can to ensure every possible angle has been addressed," Transport Minister Hishamuddin Hussein told reporters near the Kuala Lumpur International Airport.

"We are looking for accurate information from the Malaysian military. They are waiting for information from the Vietnamese side," he said.

Vietnam's state-run Tuoi Tre news also quoted Admiral Ngo Van Phat as qualifying his earlier remarks about a crash site having been identified, saying he had been referring to a presumed crash site beneath the plane's flight path using information supplied by Malaysia.

Meanwhile, Chinese relatives of the missing passengers angrily accused the airline of keeping them in the dark, while state media criticised the carrier's poor response.

Relatives were taken to a hotel near Beijing airport, put in a room and told to wait for information from the airline, but none came. About 20 people stormed out of the room at one point, enraged they had been given no information.

"There's no one from the company here, we can't find a single person. They've just shut us in this room and told us to wait," said one middle-aged man, who declined to give his name.

"We want someone to show their face. They haven't even given us the passenger list," he said.

Another relative, trying to evade a throng of reporters, muttered: "They're treating us worse than dogs."

Amid chaotic scenes, an unidentified Malaysia Airlines official spoke to reporters for just a few minutes without taking questions before leaving.

"We are working with authorities who have activated the search and rescue teams," the official said. "Our thoughts and prayers are deeply with the affected passengers and their family members."

Adding to the confusion, the official mentioned a rumour that the Chinese government has already denied - that the aircraft had landed in the southern Chinese city of Nanning.

"There have been speculations that the aircraft has landed in Nanning. We are working to verify the authenticity of the report of others," the official said.

Some Chinese media reported that he meant a place in Vietnam called Nanming. It was unclear exactly what he was talking about.

Chinese media outlets took to their official Weibo microblogs to criticise the airline for taking so long to announce what was going on and for refusing to answer questions.

"Malaysia Airlines, why did you wait for five hours after losing contact with the aircraft to first announce the news, and why did you only have a news conference after almost 13 hours?" the official Xinhua news agency wrote on one of its Weibo accounts.

Sanved Kolekar, an Indian working in Beijing, stood stunned at the airport where he was waiting for his parents who were coming over on a visit.

"My parents are on the flight, they were supposed to come here at 6.30, I don't know what happened," he said. "They haven't given me any information, it's very difficult because I don't understand the local language."

The airline said people from at least 14 nationalities were among the 227 passengers - at least 152 Chinese, 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans. Two infants were on board.

A crash, if confirmed, would mark the US-built Boeing 777-200ER airliner's deadliest incident since entering service 19 years ago.

The plane disappeared without giving a distress signal - a chilling echo of an Air France flight that crashed into the South Atlantic on June 1, 2009, killing all 228 people on board. It vanished for hours without issuing a distress call.

Flight MH370, operating a Boeing 777-200ER aircraft, last had contact with air traffic controllers 120 nautical miles off the east coast of the Malaysian town of Kota Bharu, Malaysia Airlines chief executive Ahmad Jauhari Yahya said in a statement read to an earlier news conference in Kuala Lumpur.

Flight tracking website flightaware.com showed the plane flew northeast over Malaysia after takeoff and climbed to an altitude of 35,000 feet. The flight vanished from the website's tracking records a minute later while it was still climbing.

Malaysia and Vietnam were conducting a joint search and rescue, he said but gave no details. China and the Philippines have sent ships to the South China Sea to help in any search and rescue.

"We are extremely worried," Chinese Foreign Minister Wang Yi told reporters in Beijing before the initial Vietnamese report that the plane had crashed. "The news is very disturbing. We hope everyone on the plane is safe."

The flight left Kuala Lumpur at 12.21 a.m. (1621 GMT Friday) but no trace had been found of the plane more than eight hours after it was due to land in the Chinese capital at 6.30 a.m. (2230 GMT Friday) the same day.

"We deeply regret that we have lost all contacts with flight MH370," Jauhari said.

If it is confirmed that the plane has crashed, the loss would mark the second fatal accident involving a Boeing 777 in less than a year and by far the worst since the jet entered service in 1995.

Boeing said it was aware of reports that the Malaysia Airlines plane was missing and was monitoring the situation but had no further comment. The flight was operating as a China Southern Airlines codeshare.

An official at the Civil Aviation Authority of Vietnam (CAAV) said the plane had failed to check in as scheduled at 1721 GMT while it was flying over the sea between Malaysia and Ho Chi Minh city.-Reuters