Sydney, March 26 : Authorities have warned that Tropical Cyclone Narelle will hit Australia's northwest coast as a severe Category 4 storm after sweeping across the country.

The Bureau of Meteorology (BoM) said in an update at 5 a.m. Australian Western Standard Time on Thursday (2100 GMT on Wednesday), Tropical Cyclone Narelle was 240 km off the north coast of Western Australia (WA) and steadily intensifying.

It said that the cyclone was at Category 3 strength as of Thursday morning and expected to reach Category 4 before impacting the northwest coast of the remote Pilbara region from Thursday night, bringing very destructive wind gusts of up to 275 km per hour and heavy rainfall.

The WA Department of Fire and Emergency Services (DFES) has issued an emergency alert for a 600 km stretch of coast, urging people to prepare to take shelter and charge mobile devices in case power goes out.

"There is a possible threat to lives and homes as a cyclone is approaching the area," it said.

The emergency warning zone encompasses Karratha, the largest city in the Pilbara region, with a population of approximately 22,000 people.

Schools were closed on Thursday, and Qantas and Virgin Australia have canceled flights in and out of the airport in Port Hedland, the second-largest population center in the region and the site of Australia's highest tonnage port, Xinhua news agency reported.

Tropical Cyclone Narelle hit the far north of the east coast state of Queensland as a Category 4 storm on March 20 and the Northern Territory as a Category 3 storm two days later, but avoided towns and caused only minimal damage.

More than 100 millimeters (4 inches) of rain fell across a wide area of the Northern Territory during Narelleâ??s passage, according to news reports. Australiaâ??s BOM warned of minor to major flooding of several rivers. The storm arrived amid a severe wet season in the region that had already caused damaging floods and prompted evacuations.

/IANS