Thousands of holidaymakers and locals were forced to flee to beaches in fire-ravaged southeast Australia on Tuesday, as blazes continued to rip through popular tourist areas leaving no escape by land.Some 4 000 people were trapped on the foreshore of the town of Mallacoota and many others sought refuge on beaches in fire-encircled seaside towns up and down a 200km strip of coast.Some residents with boats even took to the sea, hoping for refuge from one the worst days yet in Australia's months-long bushfire crisis.Dozens of properties were feared to have been destroyed since late Monday and at least seven people were unaccounted for in New South Wales and Victoria states as flames reached well-populated towns like Batemans Bay.In some places the blazes were so intense, the smoke so thick and the fire-provoked dry lightning storms so severe that aerial reconnaissance and waterbombing had to be halted, the New South Wales Rural Fire Service said.In Mallacoota, smoke turned day to night and the authorities said nearby fires were causing extreme thunderstorms and "ember attacks".READ | Tourists, firefighters flee as new heatwave fans Australia blazes"We've got a fire that looks like it's about to impact on Mallacoota," Victoria's Emergency Management Commissioner Andrew Crisp told public broadcaster ABC, adding that firefighters had been deployed to protect the group.Authorities had for days been warning tens of thousands of tourists enjoying Australia's summer holidays to leave the area but for thousands it was now too late to leave."We've got three strike teams in Mallacoota that will be looking after 4 000 people down on the beach there," Crisp said. "We're naturally very concerned about communities that have become isolated."Preparations were reportedly under way for an evacuation by sea or air if needed.On social media, residents said they fled on boat or were putting on life jackets in case they need to seek refuge from the fire in the water.Australia's unprecedented bushfires have been burning for months, but the latest in a series of heatwaves and high winds have wrought new devastation.The crisis has hit cities like Sydney and Melbourne, home to several million people.On Monday, around 100 000 people were urged to flee five Melbourne suburbs as the spiralling bushfire crisis killed a volunteer firefighter battling a separate blaze in the countryside.ALSO READ | Two firefighters killed battling Australian bushfiresAuthorities in the country's second-biggest city downgraded an earlier bushfire emergency warning but said residents should steer clear of the blaze, which has burned through 40 hectares of grassland.While conservative Prime Minister Scott Morrison belatedly acknowledged a link between the fires and climate change, he has continued his staunch support of Australia's lucrative coal mining industry and ruled out further action to reduce emissions.Sydney was again shrouded in toxic bushfire haze Tuesday. City officials said Sydney's New Year's Eve fireworks would go ahead, but a similar event has been cancelled in Canberra and several regional towns.