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

McCullough died Thursday in a 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, intellectually 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. The Outback melodrama about a priest's struggle between church and love won four Golden Globe awards.

During the 1980s, she wrote love stories including "An Indecent Obsession" and "The Ladies of Missalonghi."

Her historical seven-novel series "Masters of Rome" was published from 1990 to 2007.

McCullough was born in the small town of Wellington in New South Wales state on June 1, 1937. The family moved to the state capital, Sydney, where she began studying at Sydney University to become a medical doctor until she discovered that she had an allergic reaction to the antiseptic soap that surgeons use to scrub.

She switched her studies to 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 lived as an author in the United States and London before settling on Norfolk Island, a former British penal colony in the Pacific Ocean which became home to descendants of the HMS Bounty mutineers.

In 1983 she married one of those descendants, Ric Robinson, who survives her.