Defence Minister Hishammuddin Hussein told reporters Saturday that he had been informed that a Chinese satellite had spotted an object 22.5 metres (74 feet) by 13 metres (43 feet).
"The news that I just received is that the Chinese ambassador received a satellite image of a floating object in the southern corridor and they will be sending ships to verify," he said.
State broadcaster CCTV tweeted an image of the object and said it was captured around noon Tuesday, about 120 kilometres south of another satellite image that was taken days earlier of two objects in the water.
Planes and ships have been searching the area of the earlier discovery for three days but have found nothing so far. Flight 370 went missing March 8 shortly after leaving Kuala Lumpur en route to Beijing with 239 people on board.
After about a week of confusion, authorities said pings sent by the Boeing 777 for several hours after it disappeared from air traffic control screens indicated that the plane ended up in one of two huge arcs: a northern corridor stretching from Malaysia up to Central Asia, or a southern corridor that stretches in an arch toward Antarctica.
Military planes and civilian planes have already been searching about 2,500 kilometres (1,550 miles) southwest of Australia, and two military planes from China arrived Saturday in Perth to join Australian, New Zealand and U.S. aircraft in the search. Japanese planes will arrive Sunday and ships were in the area or on their way.
Griffith reported from Perth, Australia. Associated Press writers Todd Pitman, Scott McDonald and Eileen Ng in Kuala Lumpur, Malaysia contributed to this report.