Malaysia says the search for a missing passenger jet is under way along both the northern and southern corridors of where it is believed to have been deliberately diverted.
Defense Minister Hishammuddin Hussein says 26 countries are involved in the search on land and in the water. The search spans tens of millions of square kilometers.
"Today I can confirm that the search-and-rescue operations in the northern and southern corridors have already begun. Countries including Malaysia, Australia, China, Indonesia and Kazakhstan have already initiated search-and-rescue operations. The (Malaysian) Royal Air Force and the Royal National Navy have deployed assets to the southern corridor."
China has offered 21 of its satellites to help Malaysia in the unprecedented hunt for the missing Boeing 777 carrying 239 people, two-thirds of whom were Chinese nationals. But despite the help, Beijing's foreign ministry Monday leveled a new attack on Malaysia's handling of the investigation.
"Of course the current search and rescue efforts have become even harder now, and the area is much bigger. It calls for better methods. So we hope the Malaysian side can provide more thorough, accurate information to countries participating in the search and rescue, be able to further increase the search area and strengthen search efforts.''
Investigators believe the aircraft flew either north toward Central Asia or south, deeper into the vast Indian Ocean, in the hours after it mysteriously vanished on March 8.
Also Monday, a United Nations spokesman, Stephane Dujarric, said the Comprehensive Test Ban Treaty Organization, based in Vienna, confirmed last week that neither an explosion nor a plane crash on land or on water has been detected so far. The organization records seismic shocks and sound waves around the world to detect nuclear explosions, but it also can detect the explosion of a large aircraft as well as its impact on ground or water.
Australian Prime Minister Tony Abbott on Monday agreed to take charge of the southern section of the search, at the request of Malaysian Prime Minister Najib Razak.
"He asked that Australia take responsibility for the search in the southern vector, which the Malaysian authorities now think was one possible flight path for this ill-fated aircraft. I agreed that we would do so. I offered the Malaysian prime minister additional maritime surveillance resources, which he gratefully accepted."
But he added that his country has not seen any signs that the flight carrying 239 people had come close to Australian airspace.
Malaysian Defense Minister Hishammuddin denied holding back crucial information.
Meanwhile, Malaysian investigators are more closely examining the final moments before the plane disappeared from civilian radar.
Malaysia Airlines CEO Ahmad Jauhari Yahya says the last known message from the cockpit - a calm, "All right, goodnight" - is believed to have come from the plane's co-pilot.
But investigators now say it is not clear whether the radio transmission came before or after a signaling system was partially disabled or switched off, allowing the plane to further avoid detection.
The voice in the cockpit did not mention any trouble on board, suggesting he may have been misleading ground control or acting under coercion by someone familiar with aviation technology.
Authorities are also investigating the pilots and engineers who may have had contact with the plane before it left Kuala Lumpur.
The missing passenger plane was flying from Kuala Lumpur to Beijing when it disappeared.