Australian authorities said Friday they would widen the underwater hunt for missing flight MH370, as the deep-sea search for wreckage at the suspected crash site neared completion with no results.

Mini-submarine Bluefin-21 has scanned 95 percent of its initial search area in the Indian Ocean, far off western Australia, without making any "contacts of interest" the Perth-based search coordination centre said Friday.

"If no contacts of interest are made, Bluefin-21 will continue to examine the areas adjacent" to the current search zone, the statement said.

The unmanned Bluefin's current search area covers a 10-kilometre (six-mile) radius around the point where a signal consistent with those from an airplane black box was detected, the statement added.

"We are currently consulting very closely with our international partners on the best way to continue the search into the future," it said.

The Beijing-bound Malaysia Airlines flight with 239 people aboard disappeared shortly after take-off from Kuala Lumpur on March 8.

Based on satellite data analysis, it is believed to have veered far off course and crashed into a remote area of the southern Indian Ocean.

- Families vent anger -

Many family members, especially those in China -- two-thirds of the passengers were Chinese -- have for weeks bitterly accused Malaysia of a secretive and incompetent MH370 response.

Dozens of Chinese relatives held an overnight protest outside the Malaysian embassy in Beijing, according to a spokesman for relatives.

Tensions had boiled over at a briefing Thursday at a hotel where relatives are staying, after airline representatives said a Malaysian embassy official would not arrive to answer their often extremely combative questions.

"We want somebody from the embassy to come out and tell us why they didn't come," said relative Steven Wang.

He said about 100 people had waited outside the mission overnight into Friday morning.

Wang said on an online messaging forum later Friday that an official from the embassy had taken a protest letter from relatives, but had not met with them.

He added that the protest had dispersed and the families had returned to their hotel.

Chinese foreign ministry spokesman Qin Gang said Friday that his country urged Malaysia to "take seriously" the families' grievances.

He reiterated that China had been in close communication with Malaysian officials and had made "all-out efforts" to find the Boeing 777 and console passengers' families.

Dozens of relatives staged a noisy protest last month at the embassy -- apparently sanctioned by Chinese authorities, who cleared streets for their approach -- decrying Malaysian authorities and the national airline as "murderers".

- MH370 report to be released -

Malaysian Prime Minister Najib Razak has promised that a preliminary report submitted to the UN's aviation body would be released publicly.

"In the name of transparency, we will release the report next week," he told CNN in an interview aired late Thursday.

The UN's International Civil Aviation Organisation (ICAO) requires countries to submit within 30 days a factual account of what is known so far in any air crash.

A Malaysian official had said Wednesday it was uncertain whether the government would release the report.

But Najib confirmed Malaysia would make it publicly available after an "internal investigation team" examined it.

Asked on CNN whether that indicated it contained embarrassing revelations, Najib replied, "No, I don't think so."

Malaysia has pledged that any data eventually recovered from the plane's flight data recorder, known as the "black box", will be publicly released.

It has said it is assembling what officials insist will be an independent international team operating under ICAO guidelines to conduct a comprehensive probe.

Australian and Malaysia authorities insist the search -- estimated to have cost at least $100 million and counting -- will go on, possibly using other assets including more powerful sonar devices.

Najib stressed that his government was not yet prepared to declare MH370's passengers dead, while saying, "it is hard to imagine otherwise".

A relatives' organisation this week denounced a Malaysian official's suggestion that death certificates could soon be issued. The outraged families said that would be premature in the absence of any proof of what happened.

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