Malaysia has been criticised at home and abroad for announcing that a missing passenger jet with 239 people aboard had been lost at sea, even before any wreckage was found.
The country's flag carrier was also criticised for informing some relatives of the plane's loss by text message, although it insisted this had been a "last resort".
A sombre Prime Minister Najib Razak said that Malaysia Airlines Flight MH370, which vanished more than two weeks ago, had "ended in the southern Indian Ocean".
Malaysian authorities have come in for repeated criticism for perceived secretiveness and contradictory information since the plane fell off air traffic control screens on March 8 on a flight from Kuala Lumpur to Beijing.
Najib's announcement drew further criticism.
Scores of Chinese relatives marched on Malaysia's embassy in Beijing yesterday, shouting slogans including "The Malaysian Government are murderers".
And China's Government demanded authorities in Kuala Lumpur hand over the new satellite data.
Malaysia Airlines insisted that it was doing its best to handle relatives with care and dignity, and had tried to spread Najib's message with tact before the Prime Minister spoke.
"Wherever humanly possible, we did so in person with the families or by telephone, using SMS only as an additional means of ensuring fully that the nearly 1000 family members heard the news from us and not from the media," said airline chief executive Ahmad Jauhari Yahya.
The carrier added that it had deployed more than 700 "dedicated caregivers" to support the next-of-kin, who have been given hotel accommodation as well as initial financial assistance of US$5000 ($5850) per passenger.