Australians were bracing Monday for what officials warned could be the worst fire danger day ever seen, as police searched for some 100 people still missing in ravaged Tasmania.

Prime Minister Julia Gillard urged Australians to be vigilant in coming days, with scorching temperatures predicted in several states and hundreds of blazes already raging.

Several people were missing and feared dead Sunday after wildfires swept through the Australian island state of Tasmania, destroying more than 100 homes and forcing thousands to flee.

Acting Tasmania police commissioner Scott Tilyard said officers were investigating several reports of missing persons after fires ravaged the south of the state.

A gigantic, bright yellow rubber duck floated into Sydney's Darling Harbor on Saturday as part of the Australian city's annual arts festival, a celebration where high-art meets popular entertainment.

Each January hundreds of thousands of people attend theatre, music, dance, film, talks and other events for three weeks, often braving sweltering summer temperatures and thunderstorms for their dose of culture.

Australia's southern island of Tasmania has experienced its hottest day since records began, with the capital Hobart sweltering at 41.8 Celsius (107.2 Fahrenheit) on Friday.

The Bureau of Meteorology said the temperature in Tasmania, where records have been kept since the early 1880s, beat the previous high of 40.8 Celsius set in January 1976.

Australians who take part in the fighting in Syria face up to 20 years in jail, a spokesman for Foreign Minister Bob Carr said Friday after a Melbourne man was reportedly killed in the conflict.

The spokesman said the government was aware of reports that more than 100 Australians had engaged in the conflict since 2011 but he had "no evidence" of any citizens currently involved.

Australian supermarkets and pharmacies were running out of popular baby formula Thursday after unprecedented sales reportedly due to Chinese customers trying to secure supplies.

Nutricia, supplier of top-selling formula brand Karicare, said there had been a sudden surge in demand for its products which had seen stocks plummet and left shelves empty.

Australian scientists mapping the Great Barrier Reef have discovered corals at depths never before thought possible, with a deep-sea robot finding specimens in waters nearly as dark as night.

A team from the University of Queensland's Seaview Survey announced the unprecedented discovery 125 meters (410 feet) below the surface at Ribbon Reef, near the Torres Strait and at the edge of the Australian continental shelf.

Asian capital cities brought in the New Year in spectacular style after Sydney set off a global wave of fireworks, with long-isolated Yangon joining the pyrotechnic partying for the first time.

Australia's famous harbor city brought in the New Year on a balmy summer night with a US$6.9 million display curated by pop icon Kylie Minogue.

Two Australian DJs who made a hoax call to a hospital treating Prince William's pregnant wife Catherine are unlikely to face prosecution, police said Friday.

Indian-born nurse Jacintha Saldanha was found dead three days after transferring the call to a colleague this month at a London hospital who divulged details about Kate's recovery from severe morning sickness.

Australia and China are planning joint military exercises which may also include the United States as the nations work to ensure stability in the region, Canberra's defense chief said Thursday.

General David Hurley told The Australian newspaper the war games were "on the short-term horizon".