Vietnam authorities denied report that its rescue team had detected the signal of the missing Malaysia Airlines plane, China's state television reported on Saturday.
Earlier report said a Vietnamese official told local VNExpress that the signal has been detected from the missing flight about 220km southwest of Vietnam's southernmost coastal province of Ca Mau.
Malaysian and Vietnamese authorities were working jointly on search operations in the area and the airline could not yet confirm the plane had crashed, Malaysia Airlines chief executive Ahmad Jauhari Yahya said in a statement read to a news conference.
Flight MH 370 operating a Boeing B777-200 aircraft departed Kuala Lumpur at 12:21 am and had been expected to land in Beijing at 6:30 am the same day.
The Malaysia Airlines said there were 154 Chinese nationals aboard, including one infant. The aircraft left Kuala Lumpur International Airport at 12:41am on Saturday and was expected to land in Beijing at 0:30 am on Saturday.
"We deeply regret that we have lost all contacts with flight MH370 which departed Kuala Lumpur at 12:41am earlier this morning bound for Beijing," said Ahmad Jauhari Yahya, Malaysia Arlines group chief executive officer.
"The flight was carrying 227 passengers, including two infants,, 12 crew members," the airline said in a statement posted on its website.
"Our team is currently calling the next-of-kin of passengers and crew. Focus of the airline is to work with the emergency responders and authorities and mobilise its full support."
"Our thoughts and prayers are with all affected passengers and crew and their family members. The airline will provide regular updates on the situation," it said in a second statement.
The flight lost radar contact in airspace controlled by Vietnam in the early hours of Saturday morning.