Media playback is unsupported on your device Media caption Why are fire fighters starting more fires? Jon Donnison explains

Fire fighters in Australia's New South Wales have worked throughout the day to battle bushfires across the state, amid fears three blazes could merge.

New South Wales has been badly hit by bushfires after the hottest September on record. It has declared a state of emergency.

Early on Monday, the fire commissioner said three fires near Lithgow could be at risk of joining into one fire front.

Officials say conditions will worsen this week, with a peak on Wednesday.

NSW Rural Fire Services Commissioner Shane Fitzsimmons told a news briefing early on Monday that the State Mine fire was at risk of merging with a fire at Mount Victoria.

"Modelling indicates that there's every likelihood under the forecast weather conditions that these two fires, particularly up in the back end of the mountains will merge at some point... there is every likelihood that these two fires will join up," he said.

He added that in a "worst-case scenario" the fire could merge with a third fire at Springwood but said: "With the continued success of the fire-fighting effort, let's hope that it doesn't extend all that far eastward."

Speaking at the end of the day, he said the fires at Springwood and State Mine were still burning.

"Advice back from the Springwood fire area is that the fire... is still very active and is still burning in the valley system," he said.

At the State Mine fire, planned back-burning - a controlled burn aimed at managing a fire - had been thwarted "by the forward spread of the main fire front," he said.

Remote area teams would be working on Monday night to try to secure the Blackheath community near Mount Victoria, Mr Fitzsimmons said.

"It's a very difficult and challenging operation," he said. "They're going down very deep gorges... right down to creek lines."

Around 800 personnel from interstate fire departments are expected to arrive on Tuesday to assist in fire-fighting efforts.

Image caption Teams are faced with almost 60 fires in NSW, at least 14 of them uncontrolled

Image caption NSW declared a state of emergency on Sunday

Image caption The bushfires have come unusually early this year

Dry weather conditions had made firefighting efforts difficult on Monday, Mr Fitzsimmons added.

"The challenge is that most of the thunderstorm activity and lightning activity we are seeing is unaccompanied by any moisture."

NSW declared a state of emergency on Sunday, allowing emergency services to order mandatory evacuations, and cut gas and power supplies if needed.

Caroline Russell from Winmalee, in the Blue Mountains area, told the BBC that people were scared and getting ready to leave.

"We're about one or two streets away from the fire. So, it's extremely hot; it's very scary and it's a little bit panicked around here at the moment," she said.

"We're packed and ready to go. Everything's ready in the car. We're just waiting on the... response now as to whether we need to evacuate or not."

Exhausted fire fighters

Bushfires in Australia Australia is often hit by bushfires during summer months from December to February. Causes can be lightning, arson, power-line arcing, dropped cigarettes or controlled burns that go wrong. On 7 February 2009 a prolonged heat-wave and dry spell led to the Black Saturday bushfires in Victoria. The fires became Australia's worst natural disaster, killing 173 people and burning thousands of houses. On 16 February 1983 almost 200 fires caused devastation across parts of Victoria and South Australia. Seventy-five people died in what became known as the Ash Wednesday fires. In January 2013, parts of NSW and Tasmania were hit by fires as temperatures soared to record levels, with average national temperatures topping 40 degrees Celsius. One person died in Tasmania and several hundred buildings were destroyed.

Fire fighting efforts are set to continue this week, with weather conditions expected to be the most challenging this Wednesday, with warm weather and strong winds predicted.

One man has died - possibly of a heart attack - while trying to protect his home. Hundreds of people have been left homeless by the bushfires.

Australia's military is investigating whether a training exercise using explosives may have started the State Mine bushfire.

On Monday, an 11-year-old boy in the Port Stephens area was charged with deliberately lighting two fires on 13 October. Another boy, 15, has also been arrested over the fires, local media say, citing police.

One of the fires, at Heatherbrae, led to Newcastle Airport being shut and forced hundreds of people to evacuate, local reports said.

With hundreds of houses already destroyed disaster welfare centres have been set up where families can start the planning needed to rebuild their lives, the BBC's Jon Donnison, who is near the community of Winmalee in the Blue Mountains, reports.

Most of the fire fighters are volunteers - many look exhausted, and some have even lost their homes, our correspondent adds.