Fast-moving fire reaches NSW coast

Steven Trask and Heather McNab
Sydney has suffered another day of smoky air as bushfires burn across the state

More homes are threatened after an out-of-control bushfire burned through to the coast in southern NSW as thick smoke from blazes surrounding Sydney continues to blanket the city.

An emergency alert is in place for the 30,000-hectare Currowan bushfire near Batemans Bay on the state's south coast, which has already destroyed at least one home.

A second emergency alert was issued on Tuesday night for a bushfire burning near the northwestern outskirts of Sydney.

The 1800-hectare Three Mile fire is near the town of Wisemans Ferry and is close to the eastern boundary of the 220,000 hectare Gospers Mountain blaze.

The NSW Rural Fire Service says westerly winds are pushing spot fires ahead of the main Three Mile fire front.

"Fire is spotting ahead of the main fire front due to strong winds from the west," the RFS said on Tuesday evening.

The Currowan fire on the NSW South Coast is spreading quickly towards coastal areas around Pebbly Beach, Depot Beach and Pretty Beach.

"The fire has reached the coast in some areas," the RFS said on Tuesday evening.

"Firefighters and aircraft are working to protect homes where possible."

Residents in the Kioloa, Pretty Beach, Pebbly Beach, Depot Beach and Durras North areas have been told to seek shelter because it's too late to leave.

The Princes Highway between Dolphin Point and Batemans Bay has been closed in both directions.

Some 111 bush and grass fires were burning across NSW on Tuesday evening with about 50 uncontained.

One property west of the town of Kioloa has been confirmed destroyed by the Currowan fire, but it is currently too dangerous for authorities to carry out further damage assessments.

Emergency warnings were in place at 8pm for the Currowan fire and the Three Mile fire near Wisemans Ferry.

A fire near Cranebrook in western Sydney was downgraded to "advice" level after an emergency alert was issued briefly on Tuesday afternoon.

Watch and act alerts remained in place for fires near Warragamba Dam, Kurri Kurri, the Yengo National Park and Putty.

Sydney was ringed by bushfires on Tuesday with thick smoke settling in the city's basin.

It's forecast to linger for days, with health authorities advising those most at risk to stay indoors over the coming days.

The smoke is coming from large bushfires in the Blue Mountains and others near Warragamba Dam and in the Hawkesbury area.

A temperature inversion - where warm air overlays cooler air in the atmosphere - is trapping the smoke in the city.

Air quality was "hazardous" in Sydney's east and southwest on Tuesday but "good" in the northwest. The city is forecast to have "poor" air quality on Wednesday.

Firefighters will face another tough day of bushfire conditions on Wednesday.

Total fire bans are in place for the Greater Hunter, northern slopes and northwestern regions.

Fire danger ratings are very high up the NSW coast as well as in the southern and central ranges.