Malaysia's military chief has told reporters a radar detection in the Malacca Strait - off the west coast of Malaysia - could be that of the missing aircraft.
Rodzali Daud said the reading, which he explained needed to be corroborated, happened 45 minutes after the plane disappeared.
Malaysia's military radar detected what could have been the missing Malaysian Airlines plane in an area in the northern Malacca Strait - hundreds of miles from the spot where the plane disappeared, the air force chief has said.
Rodzali Daud told a news conference that the tracking was at 2.15am local time on Saturday, about 45 minutes after the plane with 239 people on board, disappeared.
He said the radar tracking was at a point 200 miles north-west of Penang island on Malaysia's west coast but stressed the information needed to be corroborated.
The Malaysian Transport Minister Mishamuuddin Hussein has given his assurances to the families of those on board the missing Malaysian Airlines plane, the searches will not "reduce in tempo".
Speaking at a news conference, he told reporters the search for MH370 now covers 27,000 nautical miles.
Mr Hussein explained a total of 12 countries are now involved in the search, 42 ships and 39 aircraft.
He added that more experts were now being drafted in to examine both military and civil data collected.
China's foreign ministry has said its aircraft are not conducting searches over land for a missing Malaysia Airlines aircraft but it is expanding searches at sea.
Earlier in the day the chief of China's civil aviation authority said that searches would be broadened to include land areas.
India is to assist in the hunt for missing Malaysian Airlines flight MH370, as the search is widened into the Andaman Sea.
"Malaysia and India are in contact on this since yesterday and contact points are being discussed. These contact points will ascertain what assistance is required and what India can offer," a spokesman at the Indian Foreign ministry said.
The spokesman said it had not yet been decided what area India would search in. India has a large military command in its Andaman and Nicobar islands and its navy patrols in the straits of Malacca.
A senior Malaysia Airlines's executive has said the airline has "no reason to believe" any actions by the crew caused the disappearance of the missing Boeing 777.
Hugh Dunleavy, the commercial director of Malaysia Airlines, told Reuters: "We have no reason to believe that there was anything, any actions, internally by the crew that caused the disappearance of this aircraft."
The search for the aircraft has been widened today to cover an area stretching from China to the Andaman Sea.
Vietnam is scaling back the search in Vietnamese waters for a Malaysian Airlines jetliner missing for four days, a senior Vietnamese official said.
"We still have plans to search with a few flights today, while other activities are suspended," Deputy Transport Minister Pham Quy Tieu, who heads the Vietnam search, told reporters. Tieu said searches by ships were being suspended.
He said Vietnam had asked Malaysian authorities for information about reports that the plane, carrying 239 passengers and crew, had changed direction after its last known contact on Saturday but it had yet to receive any response.
Meanwhile, China will add two planes to the search, the country's civil aviation chief said.
Malaysia's air force chief has denied a media report that the military last tracked a missing Malaysia Airlines jetliner over the Strait of Malacca, far from where it last made contact with civilian air traffic control when it disappeared four days ago.
"I wish to state that I did not make any such statements," air force chief Rodzali Daud said in a statement today.
The Strait of Malacca, one of the world's busiest shipping channels, runs along Malaysia's west coast.
The airline said on Saturday that the flight, carrying 227 passengers and 12 crew, last had contact off the northeast Malaysian coastal town of Kota Bharu.