Australia's maritime safety agency said today it had sharply reduced its search for the missing Malaysia Airlines jetliner to a 600,000 sq km (230,000 sq mile) corridor in the southern Indian Ocean, but that is still roughly the size of Spain and Portugal combined.

Strong currents and high seas are making the task more daunting, it said.

In the northern hemisphere, a separate search area is along an arc stretching from Malaysia through northern Thailand, Myanmar and China to Kazakhstan.

The Australian Maritime Safety Authority (AMSA), said the southern search field had been narrowed from 19 million sq km, based on analysis of satellite data collected from the plane by the United States National Transportation Safety Board.

AMSA had streamlined that data further to account for water movements in the days since Flight MH370 disappeared 10 days ago.

"It's the result of some analysis of the possible movement of the aircraft," John Young, general manager of the emergency response division of AMSA, told reporters. "There are some assumptions built in, including the speed of the aircraft."

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