NSW Police have charged two men with stealing firefighting equipment during Tuesday's bushfire crisis, as they probe several "suspicious" blazes around the state.

Key points: Police have charged two men with stealing firefighting equipment and another with impersonating an emergency services officer

Police have charged two men with stealing firefighting equipment and another with impersonating an emergency services officer Seven "suspicious" fires, including the ones that closed in around homes in the north Sydney suburb of Turramurra, are being investigated

Seven "suspicious" fires, including the ones that closed in around homes in the north Sydney suburb of Turramurra, are being investigated The NSW RFS said at least 50 homes were damaged in blazes on Tuesday

In a separate incident, officers also charged a 19-year-old with impersonating a firefighter and stealing equipment in Sydney's south.

It comes as police investigate seven "suspicious" fires across the state on Tuesday.

Police are appealing for information about fires at Moonbi, Berkeley, Balgownie, Turramurra, Katoomba, Morisset and the Royal National Park near Loftus.

Five people have also faced penalties over breaches of the statewide total fire ban for either using barbecues with an open flame or burning rubbish over the past 24 hours.

Police Commissioner Mick Fuller said it was hard to understand why people would take such risks in catastrophic conditions.

"Unfortunately we know there are some broken individuals out there who will maliciously light fires and we also have people out there who are just plain idiots and will try and light a barbeque on a day that it's catastrophic," he said.

"It's hard to believe what rock you are living under not to understand the difficult situation our state is in in terms of being so dry and so hot."

Fire damaged or destroyed more than 50 homes in NSW on Tuesday — at the height of the chaos, authorities issued emergency warnings for 19 separate blazes.

The two fires at Turramurra, on Sydney's North Shore drew assistance from aircraft, given its proximity to suburban homes.

Police officers at Lismore charged two men after they were found with emergency service paraphernalia including NSW Rural Fire Service (RFS) uniform patches, documentation, equipment and helmets.

Meanwhile, police said the 19-year-old was found riding a scooter in the Royal National Park, dressed as a firefighter.

A house burns in Bora Ridge on Tuesday afternoon. ( ABC News: Matt Coble )

NSW Police and fire investigators made a public appeal for more information regarding fires that may have been deliberately lit.

"It's awful. It angers every firefighter and angers everybody in the community," RFS commissioner Shane Fitzsimmons said.

"Clearly we are looking at those as suspicious, particularly the one in Loftus were there were multiple ignition points in the Royal National Park there."

Houses in South Turramurra were covered in fire retardant on Tuesday. ( AAP: Dan Himbrechts )

NSW Premier Gladys Berejiklian said anyone who deliberately lit a fire would face the "full force of the law" and that the punishment for arson exceeded 10 years in prison.

The RFS said at least 50 homes were damaged or destroyed in blazes around the state on Tuesday.

It brings the total number of homes affected by fires in NSW over the past week to more than 200.

Authorities said at least 21 people were injured in Tuesday's fire, including 13 firefighters.

"Early estimates are just as a result of yesterday's fire spread and fire activity," Commissioner Fitzsimmons said.

"We could be seeing in the order of another 50 homes damaged or destroyed as a result of those fires spreading across the landscape."

Commissioner Fitzsimmons said the state should expect below-average rainfall and above-average temperatures in the coming months.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 24 seconds 1 m 24 s Flames near Sydney homes

A prominent bushfire expert warned residents should brace for more days of potentially catastrophic bushfire risks in the coming weeks.

"It ain't over, it's as simple as that," said Ross Bradstock, the director of the Centre for Environmental Risk Management of Bushfires at the University of Wollongong.

"It looks like we're locked in this pattern at the moment of no rain and one or two major cold fronts a week."

The fronts bring hot, gusty conditions in front of them, elevating the risk of fires breaking out or spreading.

"We're probably in for a few more really bad days," Professor Bradstock said.