(CNN) -- Heavy flooding in Australia caused by torrential rains has forced mass evacuations from towns along the country's east coast, with critically-ill patients and newborns from one hospital being airlifted to safety.
The floods, which came in the aftermath of Tropical Cyclone Oswald, have killed four people so far, including a three-year-old boy who died after being hit by a falling tree in Brisbane, Australia's third largest city.
Bundaberg, a coastal town about 360 kilometers (220 miles) northwest of Brisbane, was particularly hard hit, with more than 2,000 homes inundated with water and a similar number of people evacuated, said mayor Mal Forman.
"We're like a little island. We have water either side of us and the water is flowing rapidly," Forman told CNN by telephone from his office in Bundaberg's town center.
"People are very bewildered."
Some of the town's roads were under six or seven meters of water and some one-storey houses were completely covered, Forman added.
Bundaberg's hospital was also evacuated as the flood waters continued to advance.
A spokeswoman for Australia's Department of Health said that about 130 patients were being airlifted to hospitals in Brisbane as a precaution.
If the floodwaters reached 10.1 meters, it would affect the hospital sewage system, making the hospital clinically unsafe, the spokeswoman said.
"I think they are expected to rise to 9.8 meters and that's a bit too close for comfort. We started transferring the most critical patients last night. The rest will be evacuated today."
Around 10 newborn babies and at-risk patients were taken to Brisbane in the early hours of Tuesday, while two C-130 aircraft from the Royal Australian Air Force arrived in Bundaberg later that morning to evacuate the remaining patients and some pregnant women nearing full term.
Evacuations have also been ordered in the town of Grafton in New South Wales, about 600 kilometers (370 miles) north of Sydney.
In Brisbane, residents were being asked to limit water use after a water treatment plant was clogged up by silted water.
But the city appeared to escape major flooding after waters peaked at a lower level than forecast.
An aerial photo taken above Bundaberg posted by Queensland State Premier Campbell Newman on his Twitter account showed vast swathes of land under water.
"Extent of the flooding is staggering," he said in the post.
Prime Minister Julia Gillard said that 100 Australian military personnel had been deployed to Bundaberg, where the Burnett River is expected to peak at around 9.6 meters on Tuesday, breaking a 1942 record.
"Currently it's sitting at 9.525 meters, we believe it has just peaked half an hour ago. It's a record for us," Forman said.
A dozen helicopters, some equipped with night vision, were used to rescue 1,000 stranded residents, many plucked from their rooftops.
"There's debris everywhere, the trampolines are everywhere, all the kids stuff is everywhere -- it's just gone," Melissa Smith, who was among those winched to safety, told ABC News.
Residents and officials are being particularly cautious, after flooding caused by heavy rains in late 2010 and 2011 left much of Queensland, known as the "Sunshine State", under water. Those floods killed 35 people.
More areas are expected to face flooding later in the week as swollen rivers and tributaries make their way toward the coast.
Extra police have been deployed in flood-hit regions to prevent looting.