(AFP) - A wildfire on the fringes of Australia's fourth-largest city Perth has destroyed several homes and forced emergency evacuations, authorities said Tuesday, just days after the west coast city entered a coronavirus lockdown.

Firefighters are battling the out-of-control bushfire on the city's eastern fringes, where several properties are ablaze and several fields have been blackened.

Smoke from the fires sent ash falling in the Perth city centre, around 30 kilometres (18 miles) away.

Firefighters were said to be working in "extremely volatile" conditions with temperatures set to hit 37 degrees Celsius (98.6 Fahrenheit).

"The fire is currently 7,000 hectares in size with the perimetre of around 75 kilometres (47 miles)," Department of Fire and Emergency Services Deputy Commissioner Craig Waters told media.

Strong winds overnight forced significant numbers of residents to flee with hundreds expected at evacuation centres, Waters said.

Locals said they were woken by emergency alerts in the earlier hours of Tuesday.

"I think it was around 3am, we were standing from our balcony in The Vines and we could see the fire over the hill coming closer," a woman at an evacuation centre told the ABC.

Although crews were still assessing the damage, local mayor Kevin Bailey told national broadcaster ABC at least 30 homes were damaged.

One firefighter was recovering in hospital from smoke inhalation but there were no other reports of injuries, Bailey said.

The news comes as Perth entered its second full day of a five-day lockdown after a security guard at a quarantine hotel tested positive for Covid-19.

"Right now, WA is battling two different kinds of emergencies, a dangerous fire emergency and a Covid-19 lockdown emergency," Premier Mark McGowan told media.

Under the lockdown, around two million residents of the city, along with residents of nearby Peel and South-West regions, must stay at home.

Authorities believe the guard contracted the UK-strain of Covid-19 from a returned traveller quarantining in a hotel in Perth.

The UK variant is among several new strains believed to be more contagious.

Western Australia was spared the brunt of Australia's devastating 2019-2020 climate change-fuelled wildfires, which mostly ravaged the country's two most populous states, New South Wales and Victoria.

© Agence France-Presse