The Australian defence vessel Ocean Shield picked up signals twice, around 370 miles north of where two signals were detected by a Chinese ship on Saturday.
Crucially, there were two distinct pinger returns - suggesting transmissions from a flight data recorder and cockpit voice recorder on a Boeing 777 jet.
Angus Houston, the former Australian defence chief heading the search, said the information was "the most promising lead" in the search so far.
But he warned it could be days before authorities confirm if the signals are from the Malaysia Airlines flight, which vanished on March 8 with 239 people on board.
