Former staff at Giorgio Armani's fashion empire joined mourners from the worlds of business, sports and politics paying their final respects to the designer who kept Italy at the forefront of global fashion.

The death of Armani on Thursday at the age of 91 sparked an outpouring of international grief, with tributes flowing in from Hollywood celebrities and ordinary people alike.

"We are retired former employees, and it was our duty, and it was obvious that we would come here because it was a great privilege and honour to work for him," said Ornella Gagliolo.

"For all of us, he was like a father, that I can tell you," she told Reuters.

His wooden casket, adorned with white roses, was on display over the weekend at a vast exhibition space at his company's headquarters in Milan, where catwalk shows are held, surrounded by dozens of small lanterns on the floor.

Santo Versace, the entrepreneur brother of murdered designer Gianni Versace, former AC Milan and Italy soccer star Paolo Maldini and Italian former prime minister Mario Monti were among the prominent figures paying tribute.

Silvana Armani, one of his nieces and part of a tight-knit group who had worked alongside him, was also in attendance.

The doors to the building slid shut late on Sunday afternoon, and the funeral on Monday will be held privately in northern Italy.

Armani died after a five-decade career in which he built a business empire spanning from haute couture to home furnishing, with his name becoming synonymous with elegant simplicity.

He had no children but worked with a trusted group of family members and long-term confidants who are expected to carry on running the business over which he exercised tight control.