(CNN) -- Malaysia Airlines Flight 370 went down over the southern Indian Ocean, Malaysian Prime Minister Najib Razak said Monday, citing a new analysis of satellite data by a British satellite company and accident investigators, and apparently ending hopes that anyone survived.
A relative of a missing passenger briefed by the airline in Beijing said, "They have told us all lives are lost."
The Prime Minister based his announcement on what he described as unprecedented analysis of satellite data sent by the plane by British satellite provider Inmarsat and the British Air Accidents Investigation Branch. He didn't describe the nature of the analysis.
But he said it made it clear that the plane's last position was in the middle of the remote southern Indian Ocean, "far from any possible landing sites.
He begged reporters to respect the privacy of relatives.
"For them, the past few weeks have been heartbreaking," he said. "I know this news must be harder still."
The Prime Minister's statement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH370 has been lost and that none of those onboard survived."
Reporters could hear wailing from a briefing for relatives of missing passengers in Beijing. Some relatives were wheeled from the conference room on stretchers, and one group of relatives smashed the lens of a reporter's camera. A woman walked out of a briefing for relatives near Kuala Lumpur crying.
A Facebook page dedicated to the only American aboard the flight, Philip Wood, said of relatives that "our collective hearts are hurting now."
"Please lift all the loved ones of MH370 with your good thoughts and prayers," a post on the page said.
Sarah Bajc, Wood's partner, canceled all media interviews after the announcement.
"I need closure to be certain, but cannot keep on with public efforts against all odds," she wrote. "I still feel his presence, so perhaps it was his soul all along."