Joern Utzon, the Danish architect who designed the iconic Sydney Opera House in Australia, has died. He was 90.Danish architect Joern Utzon was the original designer of the Sydney Opera House but quit over arguments about design and budget. (Associated Press)

Utzon died of a heart attack in his sleep early Saturday, surrounded by family members in Denmark, his son, Kim Utzon, told the Associated Press.

"He had not been doing well these past few days, since Thursday. He had been undergoing a series of operations recently," Kim Utzon said. He declined to give details.

Utzon, who has often been compared to architecture greats such as Frank Lloyd Wright and Alvar Aalto of Finland, drew up the design for the opera house in Sydney in 1957.

But he quit the project in 1966 — seven years before it was finished — after scandals about cost blowouts and design arguments. Government-appointed architects took over and the interior was not completed to Utzon's original plan.

Although considered an architectural masterpiece, the Sydney Opera House has been criticized for poor acoustics in the Concert Hall and a lack of performance and backstage space in the Opera Theatre.

Utzon, who in recent years had been suffering from a degenerative eye condition that made him virtually blind, declined several invitations to return to Australia, citing high blood pressure.

Still, he said he wasn't bitter about the dispute over the Sydney landmark.

"It's part of education — I can't be bitter about anything in life," Utzon told AP in 1998.

Born April 9, 1918, in the Danish capital of Copenhagen, Utzon graduated from the city's Academy of Arts in 1942.

He worked in the offices of Swedish architects Paul Hedquist and Gunnar Asplund and later with Aalto in Finland, before he established his own office in Copenhagen in 1950.

Designed Kuwait City National Assembly

Utzon's earliest buildings were private homes. It came as a surprise to many when he won the competition for the Sydney Opera House in 1956.

The building, with its distinctive white roof shells resembling sails, is perched on the edge of Sydney Harbour.The Sydney Opera House in Australia. (Canadian Press)

Utzon received the prestigious Pritzker Architecture Prize in 2003 for his design of the opera house. The jury singled it out as among the most iconic buildings of the 20th century, saying it "proves that the marvellous and seemingly impossible in architecture can be achieved."

Utzon also designed the National Assembly building in Kuwait City. Constructed between 1971 and 1983, the parliament building is made of concrete and its shape evokes a series of large tents, traditional meeting places for the Bedouin nomads that live in Kuwait.

The soft-spoken Dane lived in Mallorca, off Spain's eastern coast, with his wife Lis Utzon, for several years.

Utzon and his sons, Kim and Jan, designed several projects in partnership, including a church in Bagsvaerd, a Copenhagen suburb, which opened in 1976, and a furniture and design showroom, known as Paustian, in the Copenhagen harbour, completed in 1983.

Utzon won several awards for his work, including the Order of Australia in 1985 and the Sonning Prize for contributing to European culture in 1988.

Utzon is survived by his wife and their three children, Kim, Jan and Lin, and several grandchildren. Funeral plans were not immediately announced.