Search planes were dispatched to the southern Indian Ocean on Thursday after Australian authorities announced that satellite images showed least two objects in the area that could be connected to missing Malaysia Airlines flight MH370.

Four aircraft were been sent to the area after a “possible indication of debris” was detected in satellite imagery, said the Australian Maritime Safety Authority (Amsa), which is co-ordinating the search in the southern Indian Ocean.

Amsa’s emergency response general manager, John Young, said the largest possible object had been assessed as measuring 24 metres (79ft). The satellite sightings were made 2,500km (1,500 miles) south-west of Perth.

The second of two objects possibly associated with flight MH370. Photograph: Australian government

The Australian prime minister, Tony Abbott, told parliament on Thursday that the “new and credible information” had emerged from expert analysis of satellite imagery. His announcement came 12 days after Beijing-bound MH370 went missing on 8 March shortly after taking off from Kuala Lumpur, the Malaysian capital, with 239 people on board.

Abbott said an Australian air force Orion had been diverted to look for the objects, with three more aircraft following for a more intensive follow-up search. He added that he had informed the Malaysian prime minister, Najib Razak, of the developments.

The planes returned without finding anything after the initial search. Abbott cautioned against drawing premature conclusions. “We must keep in mind the task of locating these objects will be extremely difficult and it may turn out that they are not related to the search for flight MH370.

“Nevertheless I did want to update the house on this potentially important development.”

Facebook Twitter Pinterest Tony Abbott, the Australian prime minister, announces the possible breakthrough in the search for flight MH370.

Earlier, Amsa said it had halved the search area in the Indian Ocean – albeit to an area still covering 300,000 square kilometres – and moved it closer to Perth.

Young, the Amsa chief, said after Abbott’s announcement that the objects were “relatively indistinct” on the satellite imagery but were of “reasonable size and probably awash with water … bobbing up and down in the water”.

“We have been in this business of doing search and rescue and using satellite images before,” Young said. “They do not always turn out to be related to the search even if they look good, so we will hold our views on that until they are sighted.”

Australian government map of the area being searched for wreckage from flight MH370. The yellow arrows show the course believed to ahve been followed by the plane, according to the National Transport Safety Bureau in the US. Photograph: Australian government

The Orion had reported initial poor visibility, which would hamper both air and satellite efforts. The other aircraft due to arrive later on Thursday included a New Zealand air force Orion and a United States navy P8 Poseidon.

An Australian C130 Hercules aircraft would drop marker buoys to track currents that could carry any debris elsewhere. “They will provide an ongoing reference point if the task of relocating the objects becomes protracted,” Young said.

“Royal Australian Navy warship HMAS Success is en route to the area but is some days away from this area. She is well equipped to recover any objects located and proven to be from MH370.”

Facebook Twitter Pinterest Watch the briefing by Australian authorities on the possible sighting of debris from flight MH370.

Australia’s Defence Imagery and Geospatial Organisation provided the assessment of the satellite imagery, Amsa said. A senior Australian military official, Air Commodore John McGarry, said the satellite material was credible enough to divert search efforts to the area involved.

Malaysia confirmed its prime minister had been briefed by his Australian counterpart on the possible debris sighting. “At this stage Australian officials have yet to establish whether these objects are indeed related to the search for MH370,” said Malaysia’s defence minister, Hishammuddin Hussein.

Malaysia Airlines flight MH370 went missing almost two weeks ago. Australia has taken charge of the search mission over a potential southern flight path since it was revealed that the plane appeared to have continued flying for hours after the last contact was made with Malaysian air traffic authorities.

Malaysian officials said on Wednesday that both the northern and southern search arcs delineated by analysis of satellite data – sweeping north to Kazakhstan and down to the southern Indian Ocean – remained of equal interest. On Thursday, after Abbott announced the intensive new focus of the search, Malaysian authorities responded by saying that there had been a possible new development.

The search is a multinational effort involving 26 countries. On Wednesday Barack Obama said finding out what happened to MH370 was a top priority for the United States.

The BBC suggested in a report that the investigation was focusing on the ends of the two arcs. It also suggested that the plane had continued to move between its last known radar sighting at either 2.15am or 2.40am and its last contact with a satellite was at 8.11am.

The total search area set out by Malaysian authorities, covering a total of 2.24m square nautical miles, was based on initial analysis of the signals the plane sent to satellites.

Malaysian authorities have said the missing plane’s 12 crew members have been under investigation since the aircraft disappeared and that the homes of the pilot and co-pilot have been visited twice by police. The pilot’s flight simulator was taken from his house on Sunday, the Malaysian transport ministry said.

Obama, the US president, said earlier that every available resource was being used in the search, including the FBI, the National Transportation Safety Board and other agencies dealing with aviation. Three Americans were on board the flight.

Obama added: “It’s a big piece of planet that we’re searching and sometimes these things take time, but we hope and pray that we can get to the bottom of what happened.”