Kuala Lumpur, Malaysia (CNN) -- Malaysia Airlines Flight 370 went down in 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.
A relative of a missing passenger briefed by the airline in Beijing said, "They have told us all lives are lost."
While the announcement appeared to end hopes of finding survivors more than two weeks after the flight vanished, it left many key questions unanswered, including what went wrong aboard the Beijing-bound airliner and the location of its wreckage in the deep, wild waters of the Indian Ocean.
For families, some of whom had held out hope their relatives somehow were still alive, the news appeared to be devastating. At a briefing for relatives in Beijing, some were overcome and had to be taken from a hotel on stretchers. In Kuala Lumpur, a woman walked out of a briefing for families in tears.
"My son, my daughter-in-law and granddaughter were all on board. All three family members are gone. I am desperate!" a woman said outside the Beijing briefing.
Another woman came out of the briefing room screaming, expressing doubts about the Malaysian conclusion.
"Where is the proof?" she said. "You haven't confirmed the suspected objects to tell us no one survived."
Sarah Bajc, the partner of one of three Americans aboard the flight, Philip Wood, 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."
While investigators have yet to find even a piece of the plane, the Prime Minister based his announcement on what he described as unprecedented analysis of satellite data by British satellite provider Inmarsat and the British Air Accidents Investigation Branch. He didn't describe the nature of the analysis.
But he said the data -- drawn from satellite pings the ill-fated airliner continued to send throughout its final flight -- 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."
The airline said it was making plans to fly families to Australia once wreckage is found.
How 'groundbreaking' number crunching found path of Flight 370
Debris spotted in Indian Ocean
The announcement came the same day as Australian officials said they had spotted two objects in the southern Indian Ocean that could be related to the flight, which has been missing since March 8 with 239 people aboard.
One object is "a grey or green circular object," and the other is "an orange rectangular object," the Australian Maritime Safety Authority said.
Hishammuddin Hussein, Malaysia's acting transportation minister, said Monday that Australian authorities hoped to retrieve the objects by Tuesday morning. The Australian naval ship HMAS Success was steaming toward the location at last word Monday evening.
The objects are the latest in a series of sightings, including "suspicious objects" reported earlier Monday by a Chinese military plane that was searching in the same region, authorities said.
A U.S. surveillance plane sent to follow up was unable to find the objects, and so far, none of the sightings has been definitively linked to Flight 370.
Ten aircraft -- from Australia, China the United States and Japan -- searched the area Monday.
China said Monday after the Prime Minister's announcement that it would be sending more ships to help search for the aircraft.
China has a particularly large stake in the search: Its citizens made up about two-thirds of the passengers on the missing Boeing 777.
Beijing, which has repeatedly called on Malaysian authorities to step up efforts to find the plane, repeated those calls Monday after the Prime Minister's announcement.
China is paying "high attention" to the Malaysian announcement that the plane had gone down in the ocean, and asked authorities there for "all information and evidence leading up to such a conclusion," according to a statement posted on the Chinese Foreign Ministry's website.
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Satellites focus search
Amid a vast regional search that at one point spanned nearly 3 million square miles, searchers have homed in on the southern Indian Ocean in recent days after satellite images that have spotted a variety of unknown objects in an area roughly 1,500 miles southwest of Perth, Australia.
Australia reported the first images in the area, followed by China and France.
The area also lies on a projected flight path for the aircraft calculated in part from the satellite pings sent by the plane after other communications systems had shut down.
Australian officials have repeatedly warned that the objects may not turn out to be from the missing plane. They could be containers that have fallen off cargo ships, for example.
On Saturday, searchers found a wooden pallet as well as strapping belts, Australian authorities said. Hishammuddin said Monday that wooden pallets were among the items on Flight 370. But such pallets are also common in the ocean shipping industry, so it they may be unrelated to the flight.
The investigation into the passenger jet's disappearance has already produced a wealth of false leads and speculative theories. Previously, when the hunt was focused on the South China Sea near where the plane dropped off civilian radar, a number of sightings of debris proved to be unrelated to the search.