"They are very aggressive and resulting in widespread destruction throughout the communities being affected by those fires," he said.
"We literally have many thousands of men and women dedicated to saving life and protecting as much property as they can but indeed much of the vision is already showing significant destruction and devastation. This is as bad as it gets."
Last night no deaths or serious injuries had been reported, although one firefighter had been taken to hospital. Some firefighters defending other properties had been told their own homes had been destroyed.
Bushfires, driven by conditions that pushed areas into extreme and catastrophic ratings, spread across the Blue Mountains, Southern Highlands, the Hunter Valley, and the state's Central West. Emergency warnings were in force for fires raging out of control near Newcastle, Wollongong and Nowra on the south coast, Lithgow and the Blue Mountains, and Musswellbrook in the Upper Hunter region north of Sydney.
In the Blue Mountains town of Winmalee evacuee Susan Templeman told the ABC that as many as eight homes in her street - including her own - had been burned. "Like many people, [her husband] grabbed the important things - the pets, a few photos and took off to Winmalee shops which has become an unofficial evacuation centre."
"The last report of someone in our street was they saw our house on fire and then a couple of hours later, my husband was able to get back into the street and report that our house is completely gone - it is just a ruin. The houses up and down either side of us are gone and the odd one across the road, but major devastation."
NSW Emergency Services Minister Mike Gallacher told ABC radio there had been numerous reports of substantial property loss around Springwood in the Blue Mountains caused by a fire that had jumped the Nepean River and was burning in the Penrith area.
"You only need to look out into the sky and see the bloom and ash that is hanging over Sydney," he said.
Paramedics helped evacuate people in the Blue Mountains, where the worst fears were realised as flames raged through tinder-dry, heavily wooded areas beyond the reach of fire crews. A school at Springwood was evacuated as flames headed its way and Fitzsimmons said: "Nothing short of torrential rain will ease things at the moment."
In some areas residents were warned it was too late to flee and told to bunker down in their houses. People at Yanderra were told to leave immediately and head for the nearby town of Bargo as a fire at Balmoral Village headed towards the township.
Temperatures across much of the state soared into the 30s, with scorching winds gusting to 90km/h.
Firefighters expect some relief in the next couple of days with a cold front forecast for NSW.