The southern Indian Ocean is the world's third-deepest and one of the most remote stretches of water, with little radar coverage.
Hishammuddin said on Monday that searches in both the northern and southern stretches of the arc had begun, and that countries from Australia in the south, China in the north and Kazakhstan in the west had joined the hunt.
Had the plane gone northwest to Central Asia, it would have crossed over countries with busy airspace. Some experts believe it more likely would have gone south, although Malaysian authorities are not ruling out the northern corridor and are eager for radar data that might confirm or rule out that route.
The northern corridor crosses through countries including China, India and Pakistan — all of which have said they have no sign of the plane. China, where two-thirds of the passengers were from, is providing several planes and 21 satellites for the search, Premier Li Keqiang said in a statement.
"Factors involved in the incident continue to multiply, the area of search-and-rescue continues to broaden, and the level of difficulty increases, but as long as there is one thread of hope, we will continue an all-out effort," Li said.
Indonesia focused on Indian Ocean waters west of Sumatra, air force spokesman Rear Marshall Hadi Tjahjanto said.
Australia agreed to Malaysia's request to take the lead in searching the southern Indian Ocean with four Orion maritime planes that would be joined by New Zealand and US aircraft, Australian Prime Minister Tony Abbott said.
