By Matt Siegel and A. Ananthalakshmi
PERTH/KUALA LUMPUR March 23 (Reuters) - Australia's prime minister said on Sunday there was "increasing hope" of a breakthrough in the hunt for a missing Malaysian airliner carrying 239 people, after Chinese satellite images showed what could be debris within a search area deep in the southern Indian Ocean.
The latest possible lead came as the search for Malaysian Airlines Flight MH370 entered its third week, with still no confirmed trace of the Boeing 777.
An international force resumed its search efforts on Sunday, zeroing in on two areas some 2,500 km (1,500 miles) southwest of Perth in an effort to find the object identified by China and other small debris including a wooden pallet spotted by a search plane on Saturday.
"New Chinese satellite imagery does seem to suggest at least one large object down there, consistent with the object that earlier satellite imagery discovered," Australian Prime Minister Tony Abbott told reporters in Papua New Guinea, where he is on a visit.
"Obviously we have now had a number of very credible leads and there is increasing hope, no more than hope, that we might be on the road to discovering what did happen."
The new Chinese discovery was dramatically announced by Malaysia's acting transport minister, Hishammuddin Hussein, on Saturday after he was handed a note with details during a news conference in Kuala Lumpur.
China said the object was 22 metres long (74ft) and 13 metres (43ft) wide, and spotted around 120 km (75 miles) "south by west" of potential debris reported by Australia off its west coast in the forbidding waters of the southern Indian Ocean.
The new image was captured early on March 18, China's State Administration of Science, Technology and Industry for National Defense (SASTIND) said on its website.
It could not easily be determined from the blurred images whether the objects were the same as those detected by Australia, but the Chinese photograph could depict a cluster of smaller objects, a senior military officer from one of the 26 nations involved in the search for the plane said.
The wing of a Boeing 777-200ER is approximately 27 metres long and 14 metres wide at its base, according to estimates derived from publicly available scale drawings. Its fuselage is 63.7 metres long by 6.2 metres wide.
Flight MH370 vanished from civilian radar screens early on March 8, less than an hour after taking off from Kuala Lumpur on a scheduled flight to Beijing.
Investigators believe someone on board shut off the plane's communications systems, and partial military radar tracking showed it turning west and re-crossing the Malay Peninsula, apparently under the control of a skilled pilot.
That has led them to focus on hijacking or sabotage, but they have not ruled out technical problems. Faint electronic "pings" detected by a commercial satellite suggested it flew for another six hours or so, but could do no better than place its final signal on one of two vast arcs. While the southern arc is now the main focus of the search, Malaysia says the search will continue in both corridors until confirmed debris is found.
The Australian Maritime Safety Authority (AMSA) said eight aircraft would be scouring two areas covering 59,000 square km on Sunday, following news of the Chinese discovery.
"AMSA plotted the position and it fell within yesterday's search area. The object was not sighted during yesterday's search," it said in a statement.
"AMSA has used this information in the development of the search area, taking drift modelling into account."
An Australian naval vessel is now in the area, with a small flotilla of Chinese ships heading to the search zone in the coming days. Merchant ships that had been involved in the search had been released, AMSA said.
Japan and India were also sending more planes and Australian and Chinese search and navy vessels are steaming towards the southern search zone.
The first Chinese aircraft heading to Perth to join the hunt landed at the wrong airport on Saturday, underscoring the difficulties facing the increasingly complex multinational search effort.
The Chinese aircraft will be ready to take part in searches on Monday, AMSA said. (Additional reporting by Niki Koswanage and Siva Govindasamy in Kuala Lumpur, Jason Lee in Beijing; Matt Siegel in Perth, Writing by Lincoln Feast; Editing by Michael Perry)