Record flooding on Australia's southeast coast has killed three people and cut off towns, isolating tens of thousands of residents, as officials on Thursday warned more downpours were expected over the next 24 hours.

Major flooding hit several rural towns in the Hunter and Mid North Coast regions of New South Wales, Australia's most populous state, with most of the Mid North Coast region facing further heavy rainfall through Thursday.

Police said the body of a 63-year-old man was found in a flooded home near Taree, more than 300 km (186 miles) north of Sydney, while another body believed to be that of a missing man aged in his 30s had been discovered in flood waters on Mid North Coast.

The body of a 60-year-old woman was also found in her vehicle west of Coffs Harbour, police said. Police said they were searching for a missing people.