CANBERRA, March 23-- Australia's Prime Minister Tony Abbott has expressed his condolences at news of the death of Singapore's founding Prime Minister Lee Kuan Yew overnight.

In a statement released on Monday, Abbott labelled Lee as one of the most "significant leaders of our time" who led the charge in converting post-war Singapore into the independent powerhouse it is today.

The former Singapore prime minister died at age 91 after a seven-week struggle with pneumonia.

Abbott said that his remarkable leadership, which resulted in Singapore jumping from "third world to first" and becoming a prosperous modern economy, will not be forgotten for some time.

"Fifty years ago, Lee Kuan Yew led a vulnerable, fledgling nation to independence," Abbott said on Monday.

"Thanks to his leadership, Singapore is now one of the world's most prosperous nations, a financial powerhouse, and one of the world's easiest places to do business.

"Our region owes much to Lee Kuan Yew.

"Here in Australia and beyond, leaders sought and learned from his wise counsel."

Abbott touched on the positive connections Lee held with many Australian prime ministers, and attributed the healthy relationship between the two countries as a direct result of Lee's leadership of the nation.

"As Prime Minister, Lee Kuan Yew enjoyed close relationships with successive Australian Prime Ministers and worked with them to establish the strong partnership that Singapore and Australia have today," he said.

"At every stage, Australia and Singapore have stood shoulder to shoulder. We continue to do so today, as we salute one of the significant leaders of our time."

Foreign Minister Julie Bishop echoed the Prime Minister's words, telling ABC Radio that Lee's passing was "very sad news."

"He was a towering figure in the development of Singapore, he was a huge figure on the world stage, and I know he will be greatly missed," she said on Monday.

"He had such a profound influence on Singapore -- indeed, on the Asia-Pacific -- and a giant the likes of whom we probably won' t see again."