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.
Sarah Bajc, the partner of the only American 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 out 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.
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.
The objects are the latest in a series of sightings, including "suspicious objects" reported earlier Monday by a Chinese military plane that was involved in search efforts in the same region, authorities said.
So far, nothing has been definitively linked to Flight 370.
Earlier, Hishammuddin Hussein, Malaysia's acting transportation minister, said only that "at the moment, there are new leads but nothing conclusive."
A reporter on board the Chinese plane for China's official Xinhua news agency said the search team saw "two relatively big floating objects with many white smaller ones scattered within a radius of several kilometers," the agency reported Monday.
The Chinese plane was flying at 33,000 feet on its way back to Australia's west coast when it made the sighting, the Australian Maritime Safety Authority said.
But a U.S. Navy P-8 Poseidon aircraft, one of the military's most sophisticated reconnaissance planes, that was tasked to investigate the objects was unable to find them, the authority said.
With the search in its third week, authorities have so far been unable to establish where exactly the missing plane is or why it flew off course from its planned journey from Kuala Lumpur to Beijing.
China has a particularly large stake in the search: Its citizens made up about two-thirds of the 227 passengers on the missing Boeing 777. Beijing has repeatedly called on Malaysian authorities, who are in charge of the overall search, to step up efforts to find the plane.
Malaysian and Australian authorities appeared to be more interested Monday in the two objects spotted by a Royal Australian Air Force P-3 Orion aircraft.
The Australian's navy's HMAS Success "is on scene and is attempting to locate the objects," the Australian maritime authority said.
Hishammuddin said Australian authorities had said the objects could be retrieved "within the next few hours, or by tomorrow morning at the latest."
Recent information from satellites identifying objects in the water that could be related to the plane has focused search efforts on an area roughly 1,500 miles southwest of the Australian city of Perth.
A total of 10 aircraft -- from Australia, China the United States and Japan -- were tasked with combing the search area Monday.
The aerial searches have been trained on the isolated part of ocean since last week, when Australia first announced that satellite imagery had detected possible objects that could be connected to the search.
Since then, China and France have said they also have satellite information pointing to floating debris in a similar area. The Chinese information came from images, and the French data came from satellite radar.
But Australian officials have repeatedly warned that the objects detected in satellite images 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. The use of wooden pallets is common in the airline industry, but also in the shipping industry.
Hishammuddin said Monday that Flight 370 was carrying wooden pallets, but that there was so far no evidence they are related to the ones sighted in the search area.
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.