Australia's northeast coast braces for destructive cyclone

SYDNEY (Reuters) - Australian officials were urgently evacuating hundreds of residents and warning others to bunker down in their homes on Friday as a potentially destructive cyclone approached the country's northeastern coast.

Cyclone Marcia was upgraded overnight to a category 5 system, the highest rating. It is due to cross the northeast Queensland coast within hours, with destructive winds of up to 285 kph (177 miles) expected near the core of the system, according to the Australian Bureau of Meteorology.

"Over the next 24 hours, Queenslanders are about to go through a harrowing and terrifying experience," Queensland state Premier Annastacia Palaszczuk told reporters in an emergency press conference in Brisbane. "We are now very concerned with people's safety."

The cyclone is expected to bring torrential rain and flooding and massive seas, along with destructive winds.

Emergency services were urgently evacuating almost 1,000 homes in the direct path of the storm, but they warned other residents it was now too late to evacuate and urged them to bunker down in the safest place in their houses.

"We've got a small window of time to do our checks," Queensland Police Commissioner Ian Stewart said. "This is going to be a calamity."

The storm is expected to hit the coast near the town of Yeppoon, which is home to 16,000 people. After passing through low-lying areas near the coast, it is forecast to weaken to a category 3 system before hitting the city of Rockhampton, home to around 75,000. Yeppoon residents are being evacuated while Rockhampton residents have been told stay indoors.

The cyclone is expected to be accompanied by a storm surge, raising water levels around 2.6 meters (nine feet) above high tide.

Hundreds of "swift water" rescue teams were ready to assist people stranded in floodwaters, while rescue services were conducting an eleventh-hour search for two fishermen missing off Fraser Island, in the cylcone warning area.

The Port of Gladstone, Queensland's biggest multi-commodity port, ceased all ship loading operations on Thursday.

Marcia is expected to make landfall 125 km (75 miles) north of Boyne Island in Queensland, where Rio Tinto operates Australia's largest aluminium smelter.

A separate cyclone made landfall in the remote Northern Territory early Friday. The category 4 Cyclone Lam, with wind gusts of more than 250 kph (155 mph), is moving southwest and further inland. Residents in remote communities in the sparsely populated region have been told to stay indoors.

Lam will pass close to Rio's Gove bauxite mining operation. It is also threatening to disrupt BHP Billiton's Groote Eylandt manganese mine and Glencore's McArthur River zinc and lead mine.

(Reporting by Jane Wardell; Editing by Angus MacSwan and John Stonestreet)