SYDNEY (AP) -- Best-selling Australian author Colleen McCullough, whose novel "The Thorn Birds" sold 30 million copies worldwide, has died at age 77 after a long illness.

Australian author Colleen McCullough in 1977 (AP Photo/File)

McCullough died Thursday in hospital on remote Norfolk Island, HarperCollins Australia publishing director Shona Martyn said in a statement.

McCullough had continued producing books despite a string of health and eyesight problems by using dictation, Martyn said.

"Ever quick-witted and direct, we looked forward to her visits from Norfolk Island and the arrival of each new manuscript delivered in hard copy in custom-made maroon manuscript boxes inscribed with her name," Martyn said.

McCullough wrote 25 novels throughout her career. Her final book "Bittersweet" was released in 2013.

Her first novel "Tim" was published in 1974. It became a movie starring Mel Gibson, who played a young, mentally disabled handyman who had a romance with a middle-aged woman.

Her second novel, "The Thorn Birds," published in 1977, became a U.S. television mini-series in 1983 starring Richard Chamberlain, Rachel Ward and Christopher Plummer. It won four Golden Globe awards.

Before becoming an author, McCullough studied neuroscience and spent 10 years as a researcher at Yale Medical School in the United States. She established the neurophysiology department at Sydney's Royal North Shore Hospital.

She is survived by her husband, Ric Robinson.

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