Relatives of passengers and crew have been informed of the “heartbreaking” news that Flight MH370 ended in the southern Indian Ocean.
Malaysian Prime Minister Najib Razak cited new analysis by the UK Air Accident Investigation Branch and tracking firm Inmarsat suggesting the aircraft crashed into the ocean.
Malaysia Airlines told families that it was beyond reasonable doubt that the plane, with 239 people on board, was lost and that no one had survived.
Earlier, Chinese and Australian planes reported spotting several objects in an area identified by multiple satellite images as containing possible debris from the missing airliner.
The reports boost hopes that the frustrating search in the southern Indian Ocean could turn up more clues to the jet’s fate.
Australian prime minister Tony Abbott said the crew on board an Australian P3 Orion had located two objects in the search zone - the first grey or green and circular, the second orange and rectangular.
An Australian navy supply ship, the HMAS Success, was on the scene on Monday night trying to locate and recover the objects, and Malaysia’s defence minister Hishammuddin Hussein said the vessel could reach them within a few hours or by Tuesday morning.
Separately, the crew aboard one of two Chinese IL-76 aircraft combing the search zone observed two large objects and several smaller ones spread across several square kilometres, Xinhua News Agency reported.
At least one of the items - a white, square-shaped object - was captured on a camera aboard the plane, Chinese foreign ministry spokesman Hong Lei said.
“We are still racing against time,” Mr Hong said at a ministry briefing. “As long as there is a glimmer of hope, our search efforts will carry on.”
China has redirected the icebreaker Snow Dragon towards the latest find, and that ship was due to arrive early on Tuesday.
Six other Chinese ships have been directed towards the search zone along with 20 fishing vessels that have been asked to help, Mr Hong said.
Satellite images and data released by Australia, China and France in recent days have identified possible debris in the area that may be linked to the disappearance of Malaysia Airlines Flight 370 on March 8 with 239 people on board - two-thirds of whom are Chinese.
The ocean depth in the search area ranges between 1,150 metres (3,770 feet) and 7,000 metres (23,000 feet), and the US Pacific command said it was sending a black box locator in case a debris field is located.
The Towed Pinger Locator, which is pulled behind a vessel at slow speeds, has highly sensitive listening capability so that if the wreck site is located, it can hear the black box “pinger” down to a depth of about 20,000 feet (6,100 metres), Cmdr Chris Budde, a US Seventh Fleet operations officer, said in a statement.
“This movement is simply a prudent effort to preposition equipment and trained personnel closer to the search area so that if debris is found we will be able to respond as quickly as possible since the battery life of the black box’s pinger is limited,” Mr Budde said.
An Australian defence official said an Australian navy support vessel, the Ocean Shield, was also moving into the search zone and would arrive in three or four days. The ship is equipped with acoustic detection equipment that can search for the missing plane’s black box.
There was no sign the move was linked to any breakthrough in the mystery of the plane, but rather as a preparation.
“The time for the battery life (of the ‘pinger’) is potentially only a month,” said Jason Middleton, aviation professor at the University of New South Wales in Sydney. “If debris was found, it would be terrible not have anything on site and waste time” getting a ping detector to the region. “I think they’re planning ahead and getting it ready.”
Bad weather was threatening the search efforts in the area, about 2,500 kilometres (1,550 miles) south west of Perth. Australia’s Bureau of Meteorology reported increased winds, low cloud and a reduction in visibility. On Tuesday, a cold front was expected to move through the search area from the west, bringing showers, more low cloud and less visibility. Tropical Cyclone Gillian, which is further to the north, will not impact the area.
The search was given added momentum when a French satellite detected potential debris on Sunday, after Australia and China earlier released satellite images identifying suspect objects.
Australian transport minister Warren Truss said the French radar data located the objects about 850 kilometres (520 miles) north of the current search area, and that “we need to check that out as well”.
Australian authorities had sent planes and a ship to try to locate a wooden pallet that was spotted on Saturday from a search plane, but the spotters were unable to take photos of it.
Wooden pallets are most commonly used by ships but are also used in airplane cargo holds, and an official with Malaysia Airlines said on Sunday night that the flight was, in fact, carrying wooden pallets.
The southern Indian Ocean is thought to be a potential area to find the jet because Malaysian authorities have said pings sent by the Boeing 777-200 for several hours after it disappeared indicated that the plane ended up in one of two huge arcs: a northern corridor stretching from Malaysia to Central Asia, or a southern corridor that stretches towards Antarctica.
Malaysian authorities have not ruled out any possible explanation for what happened to the jet, but have said the evidence so far suggests it was deliberately turned back across Malaysia to the Strait of Malacca, with its communications systems disabled. They are unsure what happened next.
Authorities are considering the possibilities of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or someone else on board.
Malaysia’s police chief, Inspector General Khalid Abu Bakar, reiterated at a news conference on Monday that all the passengers had been cleared of suspicion.
But he said that the pilots and crew were still being investigated. He would not comment on whether investigators had recovered the files that were deleted a month earlier from the home flight simulator of the chief pilot.
In the US, Tony Blinken, President Barack Obama’s deputy national security adviser, said on CNN: “There is no prevailing theory.
“Publicly or privately, we don’t know. We’re chasing down every theory.”