A bushfire east of Cooma, in southern NSW, is threatening homes as the state faces one of its worst fire-risk days on record.
The NSW Rural Fire Service said the 500ha scrub and grass fire at Carlaminda in the Yarrabin area was burning out of control, and an emergency alert warning has been sent by telephone to residents.
"That is now impacting on homes. We have trucks there and firefighters obviously, we've also got some water bombing aircraft," RFS spokesman Ben Shepherd told reporters in Sydney on Tuesday.
Mr Shepherd said no homes had been destroyed.
There have been other outbreaks at Bathurst, in the central west, with a fire burning near the airport there, and near Wagga Wagga, in the south, where a 870ha fire has broken containment lines.
Of the more than 100 fires burning across the state about 20 are uncontained, however all but the Yarrabin fire do not pose immediate threat to property.
Parts of southern Australia face temperatures in the mid-40s and high winds, triggering a total fire ban.
NSW Rural Fire Service Commissioner Shane Fitzsimmons said it was shaping up to be one of the worst fire danger days on record.
"You don't get conditions worse than this, we are at the catastrophic level and clearly in those areas leaving early is your safest option," he said.
Prime Minister Julia Gillard, who will get briefings on the emergency situation during the day, said it was important people kept themselves safe and that they listened to local authorities and local warnings.
"The word catastrophic is being used for good reason," she told the Seven Network.
NSW Premier Barry O'Farrell said the prime minister had phoned him on Tuesday morning offering federal resources.
A bushfire in Victoria's southwest has almost doubled in size with firefighters working overnight to stop the blaze impacting rural communities.
About 500 firefighters and 10 aircraft worked to battle the Kentbruck blaze which had burnt out 7050 hectares by Monday night, threatening the rural communities of Drik Drik and Dartmoor.
Drik Drik is now no longer under direct threat.
The Country Fire Authority is closely monitoring northern parts of the state.
More than 100 properties have been destroyed by fire in Tasmania since late last week, but authorities are warning the danger isn't over.
Tasmanian Fire Service senior station officer Phil Douglas said around 40 bushfires were burning across the state on Tuesday with concerns held for out-of-control bushfires at Lake Repulse and Forcett in the southwest.
He said strong wind gusts between 30 and 70km/h were expected to sweep across the state's south between midday and 3pm (AEDT).
No deaths have been reported but emergency services crews are conducting property-to-property searches for human remains.
In the ACT, fires are burning within containment lines in the Namadgi National Park.