A fire burning through the Royal National Park in Sydney's south has been downgraded to advice status, although thick plumes of smoke are still drifting across the city.

Two fires have been burning in the park along Sir Bertram Stevens Drive at Flat Rock and south of Wattamolla Road.

A smaller fire at Flat Rock has been extinguished by firefighters, who remain on site to mop up.

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The NSW Rural Fire Service (RFS) said the fires had burnt through more than 600 hectares.

The park remains closed due to fire activity, with access only being granted to residents, and people are being told to avoid the area.

Residents of Bundeena and Mainbair are able to able to return and leave home via Farnell Ave only, the RFS said.

Firefighters conducted back burning operations overnight to establish containment lines and slow the spread of the larger fire south of Wattamolla Road.

Today they will concentrate on the northern edge of this fire as they work to bring the fire under control.

The fire will continue to produce significant amounts of smoke that is drifting over south-western Sydney and the Illawarra.

For those needing to recover their vehicles from Bundeena, the Cronulla ferry can be used to return and then people can drive out of the park.



On a day of high temperatures, there were about 1,000 people in the national park trying to cool down at the beaches and rockpools, with all car parks full.

Firefighters, police, surf life savers and National Parks personnel worked with people at beaches in the park to manage their relocation by road and boat.



Helicopters patrolled walking tracks to make sure no-one was trapped.

'It shouldn't be this bad'

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RFS senior deputy captain John Oakley said the fire took off very quickly despite manageable conditions.

"It shouldn't be this bad yet this has really taken off," he said.

"Sydney and Illawarra are both on very high fire danger, but not on severe.

"There are no total fire bans.

"And there is a north-easterly breeze, so reasonably high humidity and not too strong a wind."

He said firefighting efforts will continue over the next few days.

Currently there are 25 tankers on scene and heavy aerial attacks taking place.

Bushwalker believes fires 'strategically' lit

Sally Langford, who was leaving the park after a bushwalk, said it was "mind-blowing" to see a few small roadside fires turn into a major threat in 10 minutes.

"We drove past the first one on our way out of the Ganawarra Farm Carpark… the grass by the side of the road was alight, and our first instinct was to pull the car over, get out, and try to stamp the fire out before it spread to the brittle undergrowth of the bush," she said.

Some cars continued to drive toward the smoke that rose over the national park. ( Instagram: sallyjayl )

Ms Langford said she and her husband then saw another small fire quadruple in size in a matter of seconds, prompting them to get in their car and drive on.

"I've never seen a bushfire take hold that quickly," she said.

She said many cars drove straight past them toward the fires despite trying to alert them to the danger through frantic hand signals.

"We were worried they didn't realise how bad it was," she said.

Afterward, Ms Langford said the pair felt "quite shaken".

"We were thinking about all the people still in the park or heading straight for it," she said.

"Thinking of the full car parks and the fact the cars might all go up in flames."



Ms Langford said she believed the fires were "clearly and strategically" lit as they were all along the same side of the road.

'Let's get out of here'

Maikel Trugilho was running team building activities in the park when the fire broke out. ( ABC News: Philippa McDonald )

Maikel Trugilho was with a group of netball players taking part in team building activities when they were evacuated.

"We had to squeeze 24 girls into this small bus," he said.

"In a matter of half an hour they managed to evacuate the whole park."

He said everyone was quite tense and a lot of dense smoke could be seen.

"It was like, let's get out of here."