A red alert has been issued for northern parts of the South Pacific nation of Vanuatu as Cyclone Pam, a category five tropical storm, nears.
Pam is already bringing winds of up to 185 km/h (115mph), said the Vanuatu Meteorological Services (VMS).
VMS forecast winds of up to 230km/h (142mph) as the cyclone ploughs along off the east coast on Friday.
Meanwhile category three Cyclone Olwyn has hit the coast of Western Australia, with wind gusts up to 195kph (120mph).
People in the WA coastal region have been warned to move to higher ground to escape dangerous flooding.
Cyclone Olwyn is seen just before hitting the WA coastline near Exmouth
'Ghost town'VMS said "very destructive winds and very rough to phenomenal seas with heavy swells" were already hitting the region, while torrential rainfall, flash flooding, landslides and storm surges were expected.
The Vanuatu National Disaster Management Office (NDMO) said Torba, Sanma, Penama, Malampa and Shefa provinces were all now under red alert, meaning they should immediately head to shelter.
The agency's acting director, Peter Korisa, told Radio New Zealand that about 1,000 people had been moved to safety in vulnerable areas, but that some more remote communities were difficult to make contact with.
The capital, Port Vila, was expected to escape the worst of the cyclone but people were being advised to move away from rivers and the sea.
Cyclone Pam caused flooding in parts of the capital, Port Vila
An official with the UN's children's agency, Unicef, said the capital had become a ghost town as people took shelter.
"The winds have definitely increased, the palm trees are blowing around like crazy, you're starting to get that kind of howling wind coming through," Alice Clements told AFP news agency.
The Vanuatu country director for Save the Children, Tom Skirrow, told AFP he was concerned about families living in shanty town areas.
"Thousands of families are living in makeshift, flimsy houses which will not withstand the immense winds and rain we're expecting. Families need to urgently evacuate to safe buildings or the results could be catastrophic."
Vanuatu is a poor island chain nation, with a population of about 246,000.
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