SYDNEY/PERTH (Reuters) - Chinese ships trawled a new area in the Indian Ocean for a missing Malaysian passenger jet on Saturday, as the search for Flight MH370 entered its fourth week amid a series of false dawns over sightings of debris.
Australian authorities coordinating the operation moved the search 1,100 km (685 miles) north on Friday after new analysis of radar and satellite data concluded the Malaysia Airlines plane travelled faster and for a shorter distance after vanishing from civilian radar screens on March 8.
A Chinese military aircraft spotted three suspicious objects on Saturday in the new search area some 1,850 km (1,150 miles) west of Perth, colored white, red and orange respectively, the official Xinhua news agency said.
That sighting follows reports of "multiple objects of various colors" by international flight crews on Friday, according to the Australian Maritime Safety Authority (AMSA). Some looked like they were from fishing boats and nothing could be confirmed until they were recovered by ships, it added.
"We're hopeful to relocate some of the objects we were seeing yesterday," Royal New Zealand Air Force Squadron Leader Flight Lieutenant Leon Fox told Reuters before flying out to the search zone on an Orion P-3. "Hopefully some of the ships in the area will be able to start picking it up and give us an indication of what we were seeing."
The Chinese navy vessel Jinggangshan, which carries two helicopters, reached the new search area early on Saturday where it was expected to focus on searching for plane surfaces, oil slicks and life jackets in a sea area of some 6,900 sq km, state news agency Xinhua reported.
Another four Chinese vessels and one from Australia were on the way but would not arrive until late in the day.
Malaysia says the Boeing 777, which vanished less than an hour into a flight from Kuala Lumpur to Beijing, was likely diverted deliberately but investigators have turned up no apparent motive or other red flags among the 227 passengers or the 12 crew.
U.S. officials close to the investigation said the FBI found nothing illuminating in data it had received from computer equipment used by MH370's pilots, including a home-made flight simulator.
The search has involved more than two dozen countries and 60 aircraft and ships but has been bedeviled by regional rivalries and an apparent reluctance to share potentially crucial information due to security concerns.
Two Malaysian military aircraft, which arrived in Perth on Saturday, are expected to join the search party for the first time on Sunday.
The Malaysian government has come under strong criticism from China, home to more than 150 of the passengers, where relatives of the missing have accused the government of "delays and deception".
More than 20 Chinese relatives staged a brief protest on Saturday outside the Lido hotel in Beijing where families have been staying for the past three weeks, demanding evidence of the plane's fate.
The peaceful protest came just days after dozens of angry relatives clashed with police after trying to storm the Malaysian embassy.
Many of Saturday's protesters carried slogans demanding the "truth" about their lost loved ones.
"They don't have any direct evidence," said Steve Wang, who had a relative on the flight. "(Their conclusion) is only based on mathematical (analysis) and they used an uncertain mathematical model. Then they come to the conclusion that our relatives are all gone."
Malaysia's acting Transport Minister Hishammuddin Hussein said his country was committed to seeing the investigation through to its final conclusion.
"What they want from us is a commitment to continue the search, and that I have given, not only on behalf of the Malaysian government but the so many nations involved," he told reporters in Kuala Lumpur after speaking with families on Saturday.
For more than a week, ships and surveillance planes had been scouring seas 2,500 km (1,550 miles) southwest of Perth, where satellite images had shown possible debris from Flight MH370. That search zone has now been abandoned.
In the first week of the search, Vietnamese, Chinese and Malaysia ships and planes concentrated their efforts in the South China Sea.
The Australian Transport Safety Bureau (ATSB) said the latest shift north was based on analysis of radar data between the South China Sea and the Strait of Malacca. At that time, the Boeing 777 was making a radical diversion west from its course.
Malaysian officials said the new search area was the result of a painstaking analysis of Malaysian military radar data and satellite readings from British company Inmarsat carried out by U.S., Chinese, British and Malaysian investigators.
Engine performance analysis by the plane's manufacturer Boeing helped investigators determine how long the plane could have flown before it ran out of fuel and crashed into the ocean thousands of miles off course, they said.
Officials close to the investigation told Reuters last week that the plane may have passed close to Port Blair, the capital of India's Andaman and Nicobar Islands, 550 miles further northwest from where Malaysia has said its military radar last detected it.
At around 319,000 sq km (123,000 sq miles) - roughly the size of Poland - the new search area is larger, but closer to Perth, allowing aircraft to spend longer on site. It is also favorable in terms of the weather as it is out of the deep sea region known as the Roaring 40s for its huge seas and frequent storm-force winds.
Searchers have perhaps a week to find debris, calculate the likely crash area and find the aircraft's voice and data "black boxes" before batteries showing their location run out.
Additional reporting by Michael Martina in Perth, Niluksi Koswanage and Rujun Shen in Kuala Lumpur, Mark Hosenball in Washington, Lincoln Feast in Sydney, Paul Carsten and Xihao Jiang in Beijing; Writing by Jane Wardell; Editing by Dean Yates and Jeremy Laurence