A powerful cyclone packing expected winds of more than 200 kilometres an hour was threatening Australia's west coast Monday, forcing towns into lockdown and shutting iron ore operations.

A red alert was issued for Port Hedland and South Hedland on Western Australia state's resource-rich but sparsely-populated Pilbara coast as the category three cyclone intensified offshore, forcing residents to batten down.

"This is a powerful system," Neil Bennett, a spokesman for the Cyclone Warning Centre in Perth told AFP, saying that winds were already building around Port Hedland to about 70 kilometres an hour (45 miles per hour).

"Right around the eye (of the storm) we could see gusts of 200 kilometres (120 mph) or more."

Cyclone Christine is set to make landfall between Karratha and Port Hedland at about midnight Monday (1300 GMT) and authorities are warning of damaging storm surges, particularly if it hits at high tide.

"Rapid and powerful flooding is likely as Severe Tropical Cyclone Christine approached the coast," the Western Australian Department of Fire and Emergency Services said in an alert.

"Tides may rise significantly above the normal high tide mark with damaging waves and very dangerous coastal inundation."

Residents under the red alert are already seeking shelter, and have been ordered to remain indoors and shut off gas, water and electricity.

"It's looking very ominous, certainly it's been very grey, we have been experiencing an increase in winds, we have been getting some strong gusts and we have been getting a little bit of rain," Port Hedland mayor Kelly Howlett told the ABC.

"We know we are expecting more and I guess that's what we are all bracing for and being prepared for."

Global miner BHP Billiton said its port and rail operations in Port Hedland had been suspended, with tie-down activities completed.

"All personnel have safely left site," it said in a statement.

Bennett said he did not expect the cyclone to become more extreme and develop into a category 4 or 5 -- the highest rating -- but said it could still cause significant damage, and would continue well inland on Tuesday.

The northwest of Western Australia has the highest tropical cyclone risk in Australia, according to the Bureau of Meteorology.

On average, two cyclones affect Western Australia each year.